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Publisher: John Wiley and Sons   (Total: 1589 journals)

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Showing 1 - 200 of 1589 Journals sorted alphabetically
Abacus     Hybrid Journal   (Followers: 12, SJR: 0.48, h-index: 22)
About Campus     Hybrid Journal   (Followers: 5)
Academic Emergency Medicine     Hybrid Journal   (Followers: 65, SJR: 1.385, h-index: 91)
Accounting & Finance     Hybrid Journal   (Followers: 47, SJR: 0.547, h-index: 30)
ACEP NOW     Free   (Followers: 1)
Acta Anaesthesiologica Scandinavica     Hybrid Journal   (Followers: 52, SJR: 1.02, h-index: 88)
Acta Archaeologica     Hybrid Journal   (Followers: 164, SJR: 0.101, h-index: 9)
Acta Geologica Sinica (English Edition)     Hybrid Journal   (Followers: 3, SJR: 0.552, h-index: 41)
Acta Neurologica Scandinavica     Hybrid Journal   (Followers: 5, SJR: 1.203, h-index: 74)
Acta Obstetricia et Gynecologica Scandinavica     Hybrid Journal   (Followers: 15, SJR: 1.197, h-index: 81)
Acta Ophthalmologica     Hybrid Journal   (Followers: 6, SJR: 0.112, h-index: 1)
Acta Paediatrica     Hybrid Journal   (Followers: 56, SJR: 0.794, h-index: 88)
Acta Physiologica     Hybrid Journal   (Followers: 6, SJR: 1.69, h-index: 88)
Acta Polymerica     Hybrid Journal   (Followers: 9)
Acta Psychiatrica Scandinavica     Hybrid Journal   (Followers: 35, SJR: 2.518, h-index: 113)
Acta Zoologica     Hybrid Journal   (Followers: 7, SJR: 0.459, h-index: 29)
Acute Medicine & Surgery     Hybrid Journal   (Followers: 4)
Addiction     Hybrid Journal   (Followers: 35, SJR: 2.086, h-index: 143)
Addiction Biology     Hybrid Journal   (Followers: 14, SJR: 2.091, h-index: 57)
Adultspan J.     Hybrid Journal   (SJR: 0.127, h-index: 4)
Advanced Energy Materials     Hybrid Journal   (Followers: 27, SJR: 6.411, h-index: 86)
Advanced Engineering Materials     Hybrid Journal   (Followers: 26, SJR: 0.81, h-index: 81)
Advanced Functional Materials     Hybrid Journal   (Followers: 51, SJR: 5.21, h-index: 203)
Advanced Healthcare Materials     Hybrid Journal   (Followers: 14, SJR: 0.232, h-index: 7)
Advanced Materials     Hybrid Journal   (Followers: 268, SJR: 9.021, h-index: 345)
Advanced Materials Interfaces     Hybrid Journal   (Followers: 6, SJR: 1.177, h-index: 10)
Advanced Optical Materials     Hybrid Journal   (Followers: 7, SJR: 2.488, h-index: 21)
Advanced Science     Open Access   (Followers: 5)
Advanced Synthesis & Catalysis     Hybrid Journal   (Followers: 17, SJR: 2.729, h-index: 121)
Advances in Polymer Technology     Hybrid Journal   (Followers: 13, SJR: 0.344, h-index: 31)
Africa Confidential     Hybrid Journal   (Followers: 21)
Africa Research Bulletin: Economic, Financial and Technical Series     Hybrid Journal   (Followers: 13)
Africa Research Bulletin: Political, Social and Cultural Series     Hybrid Journal   (Followers: 10)
African Development Review     Hybrid Journal   (Followers: 33, SJR: 0.275, h-index: 17)
African J. of Ecology     Hybrid Journal   (Followers: 16, SJR: 0.477, h-index: 39)
Aggressive Behavior     Hybrid Journal   (Followers: 15, SJR: 1.391, h-index: 66)
Aging Cell     Open Access   (Followers: 11, SJR: 4.374, h-index: 95)
Agribusiness : an Intl. J.     Hybrid Journal   (Followers: 3, SJR: 0.627, h-index: 14)
Agricultural and Forest Entomology     Hybrid Journal   (Followers: 16, SJR: 0.925, h-index: 43)
Agricultural Economics     Hybrid Journal   (Followers: 45, SJR: 1.099, h-index: 51)
AIChE J.     Hybrid Journal   (Followers: 32, SJR: 1.122, h-index: 120)
Alcoholism and Drug Abuse Weekly     Hybrid Journal   (Followers: 7)
Alcoholism Clinical and Experimental Research     Hybrid Journal   (Followers: 7, SJR: 1.416, h-index: 125)
Alimentary Pharmacology & Therapeutics     Hybrid Journal   (Followers: 33, SJR: 2.833, h-index: 138)
Alimentary Pharmacology & Therapeutics Symposium Series     Hybrid Journal   (Followers: 3)
Allergy     Hybrid Journal   (Followers: 51, SJR: 3.048, h-index: 129)
Alternatives to the High Cost of Litigation     Hybrid Journal   (Followers: 3)
American Anthropologist     Hybrid Journal   (Followers: 148, SJR: 0.951, h-index: 61)
American Business Law J.     Hybrid Journal   (Followers: 24, SJR: 0.205, h-index: 17)
American Ethnologist     Hybrid Journal   (Followers: 92, SJR: 2.325, h-index: 51)
American J. of Economics and Sociology     Hybrid Journal   (Followers: 29, SJR: 0.211, h-index: 26)
American J. of Hematology     Hybrid Journal   (Followers: 34, SJR: 1.761, h-index: 77)
American J. of Human Biology     Hybrid Journal   (Followers: 12, SJR: 1.018, h-index: 58)
American J. of Industrial Medicine     Hybrid Journal   (Followers: 16, SJR: 0.993, h-index: 85)
American J. of Medical Genetics Part A     Hybrid Journal   (Followers: 16, SJR: 1.115, h-index: 61)
American J. of Medical Genetics Part B: Neuropsychiatric Genetics     Hybrid Journal   (Followers: 4, SJR: 1.771, h-index: 107)
American J. of Medical Genetics Part C: Seminars in Medical Genetics     Partially Free   (Followers: 6, SJR: 2.315, h-index: 79)
American J. of Physical Anthropology     Hybrid Journal   (Followers: 37, SJR: 1.41, h-index: 88)
American J. of Political Science     Hybrid Journal   (Followers: 276, SJR: 5.101, h-index: 114)
American J. of Primatology     Hybrid Journal   (Followers: 15, SJR: 1.197, h-index: 63)
American J. of Reproductive Immunology     Hybrid Journal   (Followers: 3, SJR: 1.347, h-index: 75)
American J. of Transplantation     Hybrid Journal   (Followers: 17, SJR: 2.792, h-index: 140)
American J. on Addictions     Hybrid Journal   (Followers: 9, SJR: 0.843, h-index: 57)
Anaesthesia     Hybrid Journal   (Followers: 138, SJR: 1.404, h-index: 88)
Analyses of Social Issues and Public Policy     Hybrid Journal   (Followers: 9, SJR: 0.397, h-index: 18)
Analytic Philosophy     Hybrid Journal   (Followers: 18)
Anatomia, Histologia, Embryologia: J. of Veterinary Medicine Series C     Hybrid Journal   (Followers: 3, SJR: 0.295, h-index: 27)
Anatomical Sciences Education     Hybrid Journal   (Followers: 1, SJR: 0.633, h-index: 24)
Andrologia     Hybrid Journal   (Followers: 2, SJR: 0.528, h-index: 45)
Andrology     Hybrid Journal   (Followers: 2, SJR: 0.979, h-index: 14)
Angewandte Chemie     Hybrid Journal   (Followers: 220)
Angewandte Chemie Intl. Edition     Hybrid Journal   (Followers: 222, SJR: 6.229, h-index: 397)
Animal Conservation     Hybrid Journal   (Followers: 41, SJR: 1.576, h-index: 62)
Animal Genetics     Hybrid Journal   (Followers: 8, SJR: 0.957, h-index: 67)
Animal Science J.     Hybrid Journal   (Followers: 6, SJR: 0.569, h-index: 24)
Annalen der Physik     Hybrid Journal   (Followers: 5, SJR: 1.46, h-index: 40)
Annals of Anthropological Practice     Partially Free   (Followers: 2, SJR: 0.187, h-index: 5)
Annals of Applied Biology     Hybrid Journal   (Followers: 7, SJR: 0.816, h-index: 56)
Annals of Clinical and Translational Neurology     Open Access   (Followers: 1)
Annals of Human Genetics     Hybrid Journal   (Followers: 9, SJR: 1.191, h-index: 67)
Annals of Neurology     Hybrid Journal   (Followers: 47, SJR: 5.584, h-index: 241)
Annals of Noninvasive Electrocardiology     Hybrid Journal   (Followers: 1, SJR: 0.531, h-index: 38)
Annals of Public and Cooperative Economics     Hybrid Journal   (Followers: 8, SJR: 0.336, h-index: 23)
Annals of the New York Academy of Sciences     Hybrid Journal   (Followers: 5, SJR: 2.389, h-index: 189)
Annual Bulletin of Historical Literature     Hybrid Journal   (Followers: 13)
Annual Review of Information Science and Technology     Hybrid Journal   (Followers: 14)
Anthropology & Education Quarterly     Hybrid Journal   (Followers: 25, SJR: 0.72, h-index: 31)
Anthropology & Humanism     Hybrid Journal   (Followers: 17, SJR: 0.137, h-index: 3)
Anthropology News     Hybrid Journal   (Followers: 15)
Anthropology of Consciousness     Hybrid Journal   (Followers: 11, SJR: 0.172, h-index: 5)
Anthropology of Work Review     Hybrid Journal   (Followers: 11, SJR: 0.256, h-index: 5)
Anthropology Today     Hybrid Journal   (Followers: 89, SJR: 0.545, h-index: 15)
Antipode     Hybrid Journal   (Followers: 49, SJR: 2.212, h-index: 69)
Anz J. of Surgery     Hybrid Journal   (Followers: 8, SJR: 0.432, h-index: 59)
Anzeiger für Schädlingskunde     Hybrid Journal   (Followers: 1)
Apmis     Hybrid Journal   (Followers: 1, SJR: 0.855, h-index: 73)
Applied Cognitive Psychology     Hybrid Journal   (Followers: 70, SJR: 0.754, h-index: 69)
Applied Organometallic Chemistry     Hybrid Journal   (Followers: 7, SJR: 0.632, h-index: 58)
Applied Psychology     Hybrid Journal   (Followers: 206, SJR: 1.023, h-index: 64)
Applied Psychology: Health and Well-Being     Hybrid Journal   (Followers: 49, SJR: 0.868, h-index: 13)
Applied Stochastic Models in Business and Industry     Hybrid Journal   (Followers: 5, SJR: 0.613, h-index: 24)
Aquaculture Nutrition     Hybrid Journal   (Followers: 14, SJR: 1.025, h-index: 55)
Aquaculture Research     Hybrid Journal   (Followers: 31, SJR: 0.807, h-index: 60)
Aquatic Conservation Marine and Freshwater Ecosystems     Hybrid Journal   (Followers: 36, SJR: 1.047, h-index: 57)
Arabian Archaeology and Epigraphy     Hybrid Journal   (Followers: 11, SJR: 0.453, h-index: 11)
Archaeological Prospection     Hybrid Journal   (Followers: 12, SJR: 0.922, h-index: 21)
Archaeology in Oceania     Hybrid Journal   (Followers: 13, SJR: 0.745, h-index: 18)
Archaeometry     Hybrid Journal   (Followers: 27, SJR: 0.809, h-index: 48)
Archeological Papers of The American Anthropological Association     Hybrid Journal   (Followers: 15, SJR: 0.156, h-index: 2)
Architectural Design     Hybrid Journal   (Followers: 25, SJR: 0.261, h-index: 9)
Archiv der Pharmazie     Hybrid Journal   (Followers: 3, SJR: 0.628, h-index: 43)
Archives of Drug Information     Hybrid Journal   (Followers: 5)
Archives of Insect Biochemistry and Physiology     Hybrid Journal   (SJR: 0.768, h-index: 54)
Area     Hybrid Journal   (Followers: 12, SJR: 0.938, h-index: 57)
Art History     Hybrid Journal   (Followers: 245, SJR: 0.153, h-index: 13)
Arthritis & Rheumatology     Hybrid Journal   (Followers: 52, SJR: 1.984, h-index: 20)
Arthritis Care & Research     Hybrid Journal   (Followers: 27, SJR: 2.256, h-index: 114)
Artificial Organs     Hybrid Journal   (Followers: 1, SJR: 0.872, h-index: 60)
ASHE Higher Education Reports     Hybrid Journal   (Followers: 15)
Asia & the Pacific Policy Studies     Open Access   (Followers: 16)
Asia Pacific J. of Human Resources     Hybrid Journal   (Followers: 320, SJR: 0.494, h-index: 19)
Asia Pacific Viewpoint     Hybrid Journal   (Followers: 1, SJR: 0.616, h-index: 26)
Asia-Pacific J. of Chemical Engineering     Hybrid Journal   (Followers: 8, SJR: 0.345, h-index: 20)
Asia-pacific J. of Clinical Oncology     Hybrid Journal   (Followers: 6, SJR: 0.554, h-index: 14)
Asia-Pacific J. of Financial Studies     Hybrid Journal   (SJR: 0.241, h-index: 7)
Asia-Pacific Psychiatry     Hybrid Journal   (Followers: 4, SJR: 0.377, h-index: 7)
Asian Economic J.     Hybrid Journal   (Followers: 8, SJR: 0.234, h-index: 21)
Asian Economic Policy Review     Hybrid Journal   (Followers: 4, SJR: 0.196, h-index: 12)
Asian J. of Control     Hybrid Journal   (SJR: 0.862, h-index: 34)
Asian J. of Endoscopic Surgery     Hybrid Journal   (SJR: 0.394, h-index: 7)
Asian J. of Organic Chemistry     Hybrid Journal   (Followers: 6, SJR: 1.443, h-index: 19)
Asian J. of Social Psychology     Hybrid Journal   (Followers: 5, SJR: 0.665, h-index: 37)
Asian Politics and Policy     Hybrid Journal   (Followers: 12, SJR: 0.207, h-index: 7)
Asian Social Work and Policy Review     Hybrid Journal   (Followers: 5, SJR: 0.318, h-index: 5)
Asian-pacific Economic Literature     Hybrid Journal   (Followers: 5, SJR: 0.168, h-index: 15)
Assessment Update     Hybrid Journal   (Followers: 4)
Astronomische Nachrichten     Hybrid Journal   (Followers: 2, SJR: 0.701, h-index: 40)
Atmospheric Science Letters     Open Access   (Followers: 29, SJR: 1.332, h-index: 27)
Austral Ecology     Hybrid Journal   (Followers: 15, SJR: 1.095, h-index: 66)
Austral Entomology     Hybrid Journal   (Followers: 9, SJR: 0.524, h-index: 28)
Australasian J. of Dermatology     Hybrid Journal   (Followers: 8, SJR: 0.714, h-index: 40)
Australasian J. On Ageing     Hybrid Journal   (Followers: 6, SJR: 0.39, h-index: 22)
Australian & New Zealand J. of Statistics     Hybrid Journal   (Followers: 14, SJR: 0.275, h-index: 28)
Australian Accounting Review     Hybrid Journal   (Followers: 3, SJR: 0.709, h-index: 14)
Australian and New Zealand J. of Family Therapy (ANZJFT)     Hybrid Journal   (Followers: 3, SJR: 0.382, h-index: 12)
Australian and New Zealand J. of Obstetrics and Gynaecology     Hybrid Journal   (Followers: 47, SJR: 0.814, h-index: 49)
Australian and New Zealand J. of Public Health     Hybrid Journal   (Followers: 11, SJR: 0.82, h-index: 62)
Australian Dental J.     Hybrid Journal   (Followers: 7, SJR: 0.482, h-index: 46)
Australian Economic History Review     Hybrid Journal   (Followers: 5, SJR: 0.171, h-index: 12)
Australian Economic Papers     Hybrid Journal   (Followers: 31, SJR: 0.23, h-index: 9)
Australian Economic Review     Hybrid Journal   (Followers: 6, SJR: 0.357, h-index: 21)
Australian Endodontic J.     Hybrid Journal   (Followers: 3, SJR: 0.513, h-index: 24)
Australian J. of Agricultural and Resource Economics     Hybrid Journal   (Followers: 3, SJR: 0.765, h-index: 36)
Australian J. of Grape and Wine Research     Hybrid Journal   (Followers: 5, SJR: 0.879, h-index: 56)
Australian J. of Politics & History     Hybrid Journal   (Followers: 14, SJR: 0.203, h-index: 14)
Australian J. of Psychology     Hybrid Journal   (Followers: 18, SJR: 0.384, h-index: 30)
Australian J. of Public Administration     Hybrid Journal   (Followers: 406, SJR: 0.418, h-index: 29)
Australian J. of Rural Health     Hybrid Journal   (Followers: 5, SJR: 0.43, h-index: 34)
Australian Occupational Therapy J.     Hybrid Journal   (Followers: 72, SJR: 0.59, h-index: 29)
Australian Psychologist     Hybrid Journal   (Followers: 12, SJR: 0.331, h-index: 31)
Australian Veterinary J.     Hybrid Journal   (Followers: 21, SJR: 0.459, h-index: 45)
Autism Research     Hybrid Journal   (Followers: 36, SJR: 2.126, h-index: 39)
Autonomic & Autacoid Pharmacology     Hybrid Journal   (SJR: 0.371, h-index: 29)
Banks in Insurance Report     Hybrid Journal   (Followers: 1)
Basic & Clinical Pharmacology & Toxicology     Hybrid Journal   (Followers: 11, SJR: 0.539, h-index: 70)
Basic and Applied Pathology     Open Access   (Followers: 2, SJR: 0.113, h-index: 4)
Basin Research     Hybrid Journal   (Followers: 5, SJR: 1.54, h-index: 60)
Bauphysik     Hybrid Journal   (Followers: 2, SJR: 0.194, h-index: 5)
Bauregelliste A, Bauregelliste B Und Liste C     Hybrid Journal  
Bautechnik     Hybrid Journal   (Followers: 1, SJR: 0.321, h-index: 11)
Behavioral Interventions     Hybrid Journal   (Followers: 9, SJR: 0.297, h-index: 23)
Behavioral Sciences & the Law     Hybrid Journal   (Followers: 24, SJR: 0.736, h-index: 57)
Berichte Zur Wissenschaftsgeschichte     Hybrid Journal   (Followers: 10, SJR: 0.11, h-index: 5)
Beton- und Stahlbetonbau     Hybrid Journal   (Followers: 2, SJR: 0.493, h-index: 14)
Biochemistry and Molecular Biology Education     Hybrid Journal   (Followers: 6, SJR: 0.311, h-index: 26)
Bioelectromagnetics     Hybrid Journal   (Followers: 1, SJR: 0.568, h-index: 64)
Bioengineering & Translational Medicine     Open Access  
BioEssays     Hybrid Journal   (Followers: 10, SJR: 3.104, h-index: 155)
Bioethics     Hybrid Journal   (Followers: 14, SJR: 0.686, h-index: 39)
Biofuels, Bioproducts and Biorefining     Hybrid Journal   (Followers: 1, SJR: 1.725, h-index: 56)
Biological J. of the Linnean Society     Hybrid Journal   (Followers: 16, SJR: 1.172, h-index: 90)
Biological Reviews     Hybrid Journal   (Followers: 4, SJR: 6.469, h-index: 114)
Biologie in Unserer Zeit (Biuz)     Hybrid Journal   (Followers: 41, SJR: 0.12, h-index: 1)
Biology of the Cell     Full-text available via subscription   (Followers: 9, SJR: 1.812, h-index: 69)
Biomedical Chromatography     Hybrid Journal   (Followers: 6, SJR: 0.572, h-index: 49)
Biometrical J.     Hybrid Journal   (Followers: 5, SJR: 0.784, h-index: 44)
Biometrics     Hybrid Journal   (Followers: 37, SJR: 1.906, h-index: 96)
Biopharmaceutics and Drug Disposition     Hybrid Journal   (Followers: 10, SJR: 0.715, h-index: 44)
Biopolymers     Hybrid Journal   (Followers: 18, SJR: 1.199, h-index: 104)
Biotechnology and Applied Biochemistry     Hybrid Journal   (Followers: 44, SJR: 0.415, h-index: 55)
Biotechnology and Bioengineering     Hybrid Journal   (Followers: 141, SJR: 1.633, h-index: 146)
Biotechnology J.     Hybrid Journal   (Followers: 14, SJR: 1.185, h-index: 51)
Biotechnology Progress     Hybrid Journal   (Followers: 39, SJR: 0.736, h-index: 101)
Biotropica     Hybrid Journal   (Followers: 20, SJR: 1.374, h-index: 71)
Bipolar Disorders     Hybrid Journal   (Followers: 9, SJR: 2.592, h-index: 100)
Birth     Hybrid Journal   (Followers: 38, SJR: 0.763, h-index: 64)
Birth Defects Research Part A : Clinical and Molecular Teratology     Hybrid Journal   (Followers: 2, SJR: 0.727, h-index: 77)
Birth Defects Research Part B: Developmental and Reproductive Toxicology     Hybrid Journal   (Followers: 6, SJR: 0.468, h-index: 47)
Birth Defects Research Part C : Embryo Today : Reviews     Hybrid Journal   (SJR: 1.513, h-index: 55)
BJOG : An Intl. J. of Obstetrics and Gynaecology     Partially Free   (Followers: 243, SJR: 2.083, h-index: 125)

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Journal Cover Advanced Optical Materials
  [SJR: 2.488]   [H-I: 21]   [7 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Online) 2195-1071
   Published by John Wiley and Sons Homepage  [1589 journals]
  • Electroluminescence of Colloidal Quantum Dots in Electrical Contact with
           Metallic Nanoparticles
    • Authors: Hongyue Wang; Quynh Le-Van, Abdelhanin Aassime, Xavier Le Roux, Fabrice Charra, Nicolas Chauvin, Aloyse Degiron
      Abstract: The electroluminescence of a carpet of colloidal quantum dots in electrical contact with a metal nanoparticle array is investigated. The properties of the structures spectacularly differ from the well-known behavior of point sources placed at nonvanishing distances from subwavelength scatterers (robustness to quenching, coupling primarily defined by the electrical contact between the two species, etc.). This regime of short-range interactions can even be enabled with nonplasmonic inclusions made of platinum, providing an extreme case of enhanced and tailored light emission by quantum emitters in a highly absorptive environment. As a corollary, surface plasmons are not a necessary or sufficient ingredient but add functionalities that nonplasmonic structures do not possess. These findings indicate that the physics of localized light emitters in highly inhomogeneous environments is far from being fully understood and have important implications for the next generation of active metamaterials and advanced optoelectronic devices.The electroluminescence of colloidal quantum dots exhibits unexpected and technology-enabling properties when the emitters are brought in electrical contact with metallic nanoparticles. The hybridization between the two species is robust to quenching, goes beyond plasmonics, and opens up new paths for active metamaterials and other advanced optoelectronic devices.
      PubDate: 2017-12-04T08:25:40.847933-05:
      DOI: 10.1002/adom.201700658
       
  • Terahertz Modulators Based on Silicon Nanotip Array
    • Authors: Zhong-Wei Shi; Xing-Xing Cao, Qi-Ye Wen, Tian-Long Wen, Qing-Hui Yang, Zhi Chen, Wen-Sheng Shi, Huai-Wu Zhang
      Abstract: As an attractive applications of terahertz (THz) radiation, imaging with THz technique stands at the focus of current interest. THz spatial modulators are key issue for fast imaging with a single detector. Here, for the first time, the silicon nanotip (SiNT) arrays are reported that can be utilized as antireflection layers for the THz wave to achieve a low-loss and spectrally broadband optical-driven THz modulator. Compared with the modulator fabricated with bare silicon, a 2–3-time larger modulation depth is achieved in SiNT modulator. Moreover, it is found that the intrinsic THz transmission of SiNT is as high as 90%, which is much higher than that of bare silicon. The theoretical simulation results reveal that a strong antireflection effect induced from SiNT layer plays a crucial role in enhancing the properties of modulator. The SiNT-based optical-driven THz modulator with low loss and high modulation depth is promising for potential application to THz imaging.New applications in the realms of terahertz (THz) technology require versatile adaptive optics and powerful modulation techniques. Semiconductors have proven to provide fast and broadband all-optical THz wave modulation. In this work, the silicon nanotip arrays on silicon substrate are utilized as antireflection layers for the THz wave, achieving a low-loss and spectrally broadband optical-driven THz modulator with remarkably enhanced modulation depth.
      PubDate: 2017-12-04T02:37:02.518022-05:
      DOI: 10.1002/adom.201700620
       
  • Printing of Large-Scale, Flexible, Long-Term Stable Dielectric Mirrors
           with Suppressed Side Interferences
    • Authors: Carina Bronnbauer; Arne Riecke, Marius Adler, Julian Hornich, Gerhard Schunk, Christoph J. Brabec, Karen Forberich
      Abstract: Dielectric mirrors are wavelength-selective mirrors which are based on thin film interference effects. Their optical band can precisely be adjusted in width, position, and reflectance by the refractive index of the applied materials, the layers' thicknesses, and the amount of deposited layers. Nowadays, they are a well-known light management tool for efficiency enhancement in, for example, semitransparent organic solar cells (OSCs) and light guiding in organic light-emitting diodes (OLEDs). However, most of the dielectric mirrors are still fabricated by lab-scale techniques such as spin-coating or physical vapor deposition under vacuum. Large-scale, fully printed (maximum 20 × 20 cm2) dielectric mirrors with adjustable reflectance characteristics are fabricated, using temperatures of maximum 50 °C and alcohol-based inks. According to the moderate processing conditions they can be easily deposited not only on rigid glass substrates but also on flexible foils. They show high stability against humidity, light irradiation, and temperature, positioning themselves as good candidates for applications in OLEDs and OSCs. Eventually, by simulations and experiments it is verified that a moderate degree of variations in layer thickness and surface roughness can suppress side interference fringes, while not impacting the main transmittance minimum or the main reflection maximum, respectively.Dielectric mirrors with high optical quality and easily adjustable spectral characteristics are printed on large-area glass and plastic substrates. Furthermore, the mirrors exhibit high stability under humidity, heat, and light exposure. Using optical simulations, it is concluded that the transmittance in the short-wavelength region is related to the roughness of the interfaces between the separate layers.
      PubDate: 2017-12-04T02:36:39.946651-05:
      DOI: 10.1002/adom.201700518
       
  • Programming Photoresponse in Liquid Crystal Polymer Actuators with Laser
           Projector
    • Authors: Owies M. Wani; Hao Zeng, Piotr Wasylczyk, Arri Priimagi
      Abstract: A versatile, laser-projector-based method is demonstrated for programming alignment patterns into monolithic films of liquid crystal polymer networks. Complex images can be photopatterned into the polymer films with sub-100 µm resolution, using relatively short exposure times. The method is further used to devise both photochemically and photothermally driven actuators that can undergo distinct light-induced shape changes, dictated by the programmed alignment patterns. Deformation modes such as buckling and coiling, as well as miniature robotic devices such as a gripper and a light-responsive octopod, are demonstrated. The reported technique enables easy and cost-effective programmable actuation with relatively high throughput, thus significantly facilitating the design and realization of functional soft robotic actuators.Programmed photoresponses are inscribed into monolithic actuators made of liquid crystal polymer networks, using a laser projector and photoalignment technique. Distinct light-induced shape changes, such as bending, buckling, coiling, gripping, and octopus-like motion, driven by both photochemical and photothermal actuation are demonstrated. The reported technique enables easy and efficient programming in actuation, thereby significantly facilitating the realization of functional soft robots.
      PubDate: 2017-12-04T02:36:11.989514-05:
      DOI: 10.1002/adom.201700949
       
  • All-Inorganic Perovskite Quantum Dots/p-Si Heterojunction Light-Emitting
           Diodes under DC and AC Driving Modes
    • Authors: Jingjing Liu; Xuexi Sheng, Yangqing Wu, Dongke Li, Jianchun Bao, Yang Ji, Zewen Lin, Xiangxing Xu, Linwei Yu, Jun Xu, Kunji Chen
      Abstract: Light-emitting diodes based on perovskite quantum dots have attracted much attention since they can be applied in low-cost display, biosensors, and other optoelectronic devices. Here, all-inorganic light-emitting diodes based on n-type perovskite quantum dots/p-Si heterojunction are fabricated. Both the green and the red light emission are achieved at room temperature. The output power density is 0.14 mW cm−2 for green light device and 0.25 mW cm−2 for the red one. The relatively low turn on voltage and high emission intensity in red light device can be attributed to the small hole injection barrier between CsPbI3 quantum dots and p-Si. The emission drop off at high current density is observed under direct current (DC) driving mode, which is significantly improved by applying alternating current (AC) square pulses. The enhanced electroluminescence and the improved operation stability at high current density under AC driving mode can be attributed to the less thermal degradation and the reduced charge accumulation in the interface defect states due to the alternated biases. The results demonstrate the possibility of integrating the perovskite quantum dots with Si platform, which will be helpful to extend their actual applications.All-inorganic light-emitting diodes based on n-type perovskite quantum dots/p-Si heterojunction are fabricated. Both the green and the red light emission are achieved at room temperature. The enhanced electroluminescence and improved operation stability under alternating current driving mode can be attributed to the less thermal degradation and the reduced charge accumulation in the interface defects states due to the alternated biases.
      PubDate: 2017-12-04T02:35:48.180785-05:
      DOI: 10.1002/adom.201700897
       
  • Coding Metasurfaces: Beam-Editing Coding Metasurfaces Based on
           Polarization Bit and Orbital-Angular-Momentum-Mode Bit (Advanced Optical
           Materials 23/2017)
    • Authors: Qian Ma; Chuan Bo Shi, Guo Dong Bai, Tian Yi Chen, Ahsan Noor, Tie Jun Cui
      Abstract: A vector beam modulator based on a coding metasurface is presented by Tie Jun Cui and co-workers in article number 1700548 to encode information on the orthogonal linear polarization bit and orbital angular momentum (OAM) mode bit. Compared with the usual phase coding metasurfaces, the information loss in transmission by this method can be reduced dramatically because of the orthogonality among coded symbols.
      PubDate: 2017-12-01T07:34:27.236688-05:
      DOI: 10.1002/adom.201770117
       
  • Contents: (Advanced Optical Materials 23/2017)
    • PubDate: 2017-12-01T07:34:26.022123-05:
      DOI: 10.1002/adom.201770115
       
  • OLEDs: Multifunctional Phenanthroimidazole Derivatives to Realize
           High-Performance Deep-Blue and White Organic Light-Emitting Diodes
           (Advanced Optical Materials 23/2017)
    • Authors: Xiaoyang Du; Guang Li, Juewen Zhao, Silu Tao, Caijun Zheng, Hui Lin, Qingxiao Tong, Xiaohong Zhang
      Abstract: Highly efficient and stabilized white organic light emitting diodes (WOLEDs) are realized for ultrahigh exciton utilization in article number 1700498 by Silu Tao, Qingxiao Tong, and co-workers. The device uses a novel phenanthroimidazole derivative as the blue emitter as well as the host for red emitters to achieve step-wise energy transfer from the blue emitter to green and red emitters. As a consequence, a high external quantum efficiency over 19% with stable spectra is obtained.
      PubDate: 2017-12-01T07:34:25.363457-05:
      DOI: 10.1002/adom.201770113
       
  • Masthead: (Advanced Optical Materials 23/2017)
    • PubDate: 2017-12-01T07:34:24.716582-05:
      DOI: 10.1002/adom.201770116
       
  • Nonlinear Optical Materials: The Next-Generation of Nonlinear Optical
           Materials: Rb3Ba3Li2Al4B6O20F—Synthesis, Characterization, and Crystal
           Growth (Advanced Optical Materials 23/2017)
    • Authors: Hongwei Yu; Joshua Young, Hongping Wu, Weiguo Zhang, James M. Rondinelli, Shiv Halasyamani
      Abstract: In article number 1700840, structural evolution from KBe2BO3F2 (KBBF) to Rb3Ba3Li2Al4B6O20F is shown by James M. Rondinelli, Shiv Halasyamani, and co-workers. Through the judicious selection of cations, the layered crystal structure of KBBF is “transformed” to three-dimensional Rb3Ba3Li2Al4B6O20F. The 3D nature of Rb3Ba3Li2Al4B6O20F enabled us to grow large single crystals and determine that the material is nonlinear-optically active with a birefringence of 0.057 at 1064 nm and a Type I phase-matching limit of 243 nm. This suggests Rb3Ba3Li2Al4B6O20F may be used to generate 266 nm radiation.
      PubDate: 2017-12-01T07:34:24.33237-05:0
      DOI: 10.1002/adom.201770114
       
  • WO3-Based Electrochromic Distributed Bragg Reflector: Toward Electrically
           Tunable Microcavity Luminescent Device
    • Authors: Lili Xiao; Ying Lv, Jie Lin, Yongsheng Hu, Wenjie Dong, Xiaoyang Guo, Yi Fan, Nan Zhang, Jialong Zhao, Yunjun Wang, Xingyuan Liu
      Abstract: The electroresponsive WO3-based electrochromic distributed Bragg reflectors (ECDBRs) are fabricated by means of one-step, room temperature glancing-angle electron-beam evaporation. The reflectance and Bragg wavelength of ECDBRs can be precisely and reversibly tailored on a large scale by simply applying a small bias voltage (±1.1 V) due to the electrochromic effect of the WO3 layer, and this unique character is utilized to construct an electrically tunable microcavity luminescent device with embedded green CdSe@ZnS quantum dots (QDs). Therefore, large and reversible modulation in terms of photoluminescence (PL) peak intensity (18–335%), PL peak position (from 510.3 to 525.8 nm), and full width at half maximum (from 21.8 to 11.4 nm) from QDs in microcavity are achieved under electrical stimulus. The results will potentially provide a straightforward voltage-control route toward broadband tunable microcavity electroluminescent and lasing devices.The electrochromic distributed Bragg reflector based on monomaterial of WO3 with different porosity is successfully fabricated and used to construct an electrically tunable microcavity luminescent device, which shows large and reversible changes in photoluminescence and provides an instructive guidance toward electroactive optical and optoelectronic devices.
      PubDate: 2017-12-01T03:11:49.38782-05:0
      DOI: 10.1002/adom.201700791
       
  • Generation of Radial Polarized Lorentz Beam with Single Layer Metasurface
    • Authors: Jin-Ying Guo; Xin-Ke Wang, Jing-Wen He, Huan Zhao, Sheng-Fei Feng, Peng Han, Jia-Sheng Ye, Wen-Feng Sun, Guo-Hai Situ, Yan Zhang
      Abstract: A radially polarized Lorentz beam is demonstrated in the terahertz waveband with a single layer metasurface. Composed of cross antennas of various sizes and orientation, the metasurface performs simultaneously a continuous amplitude modulation and a controlled polarization spatial redistribution of incident waves of wavelength 400 µm. The metasurface device is designed and characterized using a terahertz time domain spectral imaging system. Experimental results are consistent with theoretical calculations. With the advantage of compactness and simplicity, this device may be applied to generate various complex light fields and in the reconstruction of computer-generated polarization hologram.Consecutive redistribution of polarization and transmittance is simultaneously achieved with a single layer metasurface. A sample is designed to generate a radial polarized Lorentz beam in the THz region, and the experimental results fit with simulation well. This kind of device can be used in the reconstruction of complex light field and computer generated polarization hologram.
      PubDate: 2017-12-01T03:10:55.655375-05:
      DOI: 10.1002/adom.201700925
       
  • High and Fast Response of a Graphene–Silicon Photodetector Coupled with
           2D Fractal Platinum Nanoparticles
    • Authors: Kun Huang; Yucong Yan, Ke Li, Afzal Khan, Hui Zhang, Xiaodong Pi, Xuegong Yu, Deren Yang
      Abstract: 2D material-based electronic devices like graphene–silicon photodetectors (Gr–Si PDs) have attracted much attention of researchers in the past few years. Due to the nature of Schottky junction, Gr–Si PDs have ultrafast response. However, responsivity of Gr–Si PDs is very low, which hinders their practical application. Low work function of Gr and poor absorbance of Si are mainly responsible for this problem. Here, a novel approach for coupling of Gr–Si PDs with 2D fractal platinum nanoparticles (Pt NPs) is demonstrated to enhance the responsivity and speed up the response of Gr–Si PDs at the same time. 2D morphology of fractal Pt NPs helps to overcome the coffee-ring effect. Fully covered fractal Pt NPs remarkably improve the absorption of Gr–Si PDs by plasmonic effect. Responsivity of Gr–Si PDs thus is remarkably enhanced to 26 A W−1. Meanwhile, work function of Gr is improved by the physical doping of high-work-function Pt NPs. Therefore, the Schottky barrier of Gr–Si junction is increased, resulting in faster response. Improvement in the built-in electric field reduces the background noise of Gr–Si PDs as well. These results indicate toward a simple and novel approach for fabricating high and fast response Gr–Si PDs.A novel approach to enhance the responsivity and the response speed of graphene–silicon photodetectors is demonstrated with 2D fractal platinum nanoparticles. Fully covered platinum nanoparticles improve the responsivity of photodetectors to 26 A W−1, which outperforms similar photodetectors reported so far.
      PubDate: 2017-12-01T03:10:40.60803-05:0
      DOI: 10.1002/adom.201700793
       
  • Toward High Uniformity of Photoresponse Broadband Hybrid
           Organic–Inorganic Photodiode Based on PVP-Modified Perovskite
    • Authors: Feiyu Zhao; Kun Xu, Xiao Luo, Yuanlong Liang, Yingquan Peng, Feiping Lu
      Abstract: Broadband photodiode based on Si/perovskite structure that combines the advantages of both silicon and perovskite is presented in this paper. This study addresses the issue of the absent of ultraviolet absorption of silicon and the near-infrared absorption of perovskite. More significantly, the polyvinyl pyrrolidone (PVP) modification process on the perovskite film shows efficiency on morphology and crystallizing control that are important for high uniformity of responsivity and reproducibility. The result shows high spectral uniformity of responsivity (uSR = 0.85) on a wide spectrum ranging from 405 to 808 nm and the average of deviation of reproducibility is only 2.1%. Fast response time (645 µs), good on–off switching performance, and high photosensitivity (Ion/Ioff = 1322) of the as-fabricated device are also achieved in this work. This research indicates that the high-performance broadband photodiode can be realized by the novel organic–inorganic structure and PVP modification without compromising any of its performance.Hybrid organic–inorganic photodiodes based on Si/perovskite structure and further modified with polyvinyl pyrrolidone additive are fabricated, realizing high-performance broadband photoresponse from NUV–NIR region. This study explores a new way for broadband photodetector and an efficient process of perovskite film modification.
      PubDate: 2017-11-30T09:22:16.396593-05:
      DOI: 10.1002/adom.201700509
       
  • Tin-Based Perovskite with Improved Coverage and Crystallinity through
           Tin-Fluoride-Assisted Heterogeneous Nucleation
    • Authors: Min Xiao; Shuai Gu, Pengchen Zhu, Mingyao Tang, Weidong Zhu, Renxing Lin, Chuanlu Chen, Weichao Xu, Tao Yu, Jia Zhu
      Abstract: Tin fluoride (SnF2) is widely used as an effective additive for lead-free tin-based perovskite solar cells. However, the function of SnF2 and the mechanism in improving the film morphology are still not clear. In this work, it is clearly demonstrated that SnF2 can play a crucial role in the crystal nucleation process. Due to the limited solubility, SnF2 creates more nucleuses for the crystal growth and therefore enables more uniform thin film with high coverage. It is confirmed that this mechanism can be applied to the growth of both thin film and single crystal. As a result of tin-fluoride-assisted heterogeneous nucleation, an MASnIBr2-based perovskite solar cell with a high and stable power conversion efficiency of 3.70% is demonstrated.SnF2 can serve as heterogeneous nucleation sites to facilitate crystal growth of tin-based perovskite crystal. The addition of SnF2 with appropriate concentration can enable tin-based perovskite film with full coverage and improved crystallinity and reduced carrier recombination. As a result, a tin-based PSC with stable efficiency of 3.70% is demonstrated.
      PubDate: 2017-11-30T09:21:29.858702-05:
      DOI: 10.1002/adom.201700615
       
  • High-Efficiency Dielectric Metasurfaces for Polarization-Dependent
           Terahertz Wavefront Manipulation
    • Authors: Huifang Zhang; Xueqian Zhang, Quan Xu, Chunxiu Tian, Qiu Wang, Yuehong Xu, Yanfeng Li, Jianqiang Gu, Zhen Tian, Chunmei Ouyang, Xixiang Zhang, Cong Hu, Jiaguang Han, Weili Zhang
      Abstract: Recently, metasurfaces made up of dielectric structures have drawn enormous attentions in the optical and infrared regimes due to their high efficiency and designing freedom in manipulating light propagation. Such advantages can also be introduced to terahertz frequencies where efficient functional devices are still lacking. Here, polarization-dependent all-silicon terahertz dielectric metasurfaces are proposed and experimentally demonstrated. The metasurfaces are composed of anisotropic rectangular-shaped silicon pillars on silicon substrate. Each metasurface holds dual different functions depending on the incident polarizations. Furthermore, to suppress the reflection loss and multireflection effect in practical applications, a high-performance polarization-independent antireflection silicon pillar array is also proposed, which can be patterned at the other side of the silicon substrate. Such all-silicon dielectric metasurfaces are easy to fabricate and can be very promising in developing next-generation efficient, compact, and low-cost terahertz functional devices.Polarization-dependent all-silicon dielectric metasurfaces are demonstrated for efficiently manipulating the terahertz wavefront. The proposed metasurfaces consist of rectangular silicon pillars, and each functions as two different devices with respect to the x- and y-polarizations. The efficiency of the structural interface can reach about 65%. Besides, a polarization-independent antireflection layer is proposed and characterized, which can greatly reduce the reflection loss.
      PubDate: 2017-11-30T09:20:56.221505-05:
      DOI: 10.1002/adom.201700773
       
  • Direct Investigation of the Birefringent Optical Properties of Black
           Phosphorus with Picosecond Interferometry
    • Authors: Wei Zheng; Andrei Nemilentsau, Dustin Lattery, Peipei Wang, Tony Low, Jie Zhu, Xiaojia Wang
      Abstract: Black phosphorus (BP) is an emerging 2D semiconducting material with great potential for nanoelectronic and nanophotonic applications, especially owing to its unique anisotropic electrical and optical properties. Many theoretical studies have predicted the anisotropic optical properties of BP, but the direct experimental quantification remains challenging. The difficulties stem from the ease of BP's degradation when exposed to air in ambient conditions, and from the indirect nature of conventional approaches that are subject to large measurement uncertainties. This work reports a direct investigation of the birefringent optical constants of micrometer-thick BP samples with picosecond (ps) interferometry, over the wavelength range from 780 to 890 nm. In this ps-interferometry approach, an ultrathin (5 nm) platinum layer for launching acoustic waves naturally protects the BP flake from degradation. The birefringent optical constants of BP for light polarization along the two primary crystalline orientations, zigzag and armchair, are directly obtained via fitting the attenuated Brillouin scattering signals. A biexponential model is further proposed to analyze the Brillouin scattering signals for a random incident light polarization. The BP experimental results and the associated measurement sensitivity analysis demonstrate the reliability and accuracy of the ps-interferometry approach for capturing the polarization-dependent optical properties of birefringent materials.Black phosphorus (BP) is an emerging 2D semiconducting material with unique anisotropic optical properties. This work reports a direct investigation of the birefringent optical constants of BP with picosecond-interferometry in the near-infrared regime. The birefringent optical constants of BP for light polarization along zigzag and armchair directions are obtained via analyzing the attenuated Brillouin scattering signals.
      PubDate: 2017-11-29T03:20:48.662965-05:
      DOI: 10.1002/adom.201700831
       
  • Fano Resonances in Ultracompact Silicon-on-Insulator Compatible Integrated
           Photonic–Plasmonic Hybrid Circuits
    • Authors: Zhipeng Qi; Guohua Hu, Pengfei Zheng, Ruigong Su, Wenhua Shi, Binfeng Yun, Ruohu Zhang, Yiping Cui
      Abstract: A novel on-chip Fano device is experimentally demonstrated operating at telecom wavelengths, which consists of an ultracompact plasmonic nanocavity integrated with two Si waveguides on a silicon-on-insulator substrate. It is observed that an Au symmetric split ring with a large linewidth can be coupled to an embedded Au nanorod with a narrow linewidth via excitation of an Si waveguide, contributing to a Fano resonance phenomenon. In addition, the relative precise control of the resonant properties, including the depth, lineshape, and central wavelength, is realized by varying the rotation angle of the Au nanorod. For further investigations, a coupled Lorentz oscillator model is applied to study the transmission peak arising within an absorption region in the nanocavity. Slow-light effects and sensing characteristics are also verified with finite difference time domain simulations and numerical calculations. This device has achieved Fano resonance in integrated photonic–plasmonic hybrid circuits, which may find utility in optical communications, buffering, and sensing.An integrated Fano device based on an silicon-on-insulator compatible photonic–plasmonic hybrid circuit is presented, which mainly consists of an ultracompact plasmonic nanocavity and two Si nanowire waveguides. A controllable Fano resonance is realized in this circuit, which can be explained by three coupled oscillators model. This device may find utility in optical communications, buffering, and sensing.
      PubDate: 2017-11-20T01:55:57.951877-05:
      DOI: 10.1002/adom.201700304
       
  • 2D Nonlayered Selenium Nanosheets: Facile Synthesis, Photoluminescence,
           and Ultrafast Photonics
    • Authors: Chenyang Xing; Zhongjian Xie, Zhiming Liang, Weiyuan Liang, Taojian Fan, Joice Sophia Ponraj, Sathish Chander Dhanabalan, Dianyuan Fan, Han Zhang
      Abstract: Investigations into 2D nanomaterials are of considerable significance from both an academic and industrial point of view. The present work addresses, for the first time, the fabrication of 2D nonlayered ultrathin selenium through a facile liquid-phase exfoliation method. The results reveal that the as-prepared 2D Se nanosheets are 40–120 nm in lateral dimension and 3–6 nm in thickness. The nanosheets exhibit a trigonal crystalline phase similar to their bulk counterpart, indicating the conservation of the crystalline features during the exfoliation procedure. The successful preparation of 2D Se nanosheets from nonlayered bulk Se can be ascribed to two kinds of anisotropy: (1) that of crystalline bulk Se with chain-like structures, where strong intrachain SeSe covalent bonds coexist with weak interchain van der Waals forces, and (2) that of probe sonication in the vertical direction. The results also show that the 2D Se nanosheets possess a size-dependent band gap (Eg), strong photoluminescence effect and robust, chemical stability under ambient conditions. Furthermore, a 2D Se-nanosheet-based optical modulation device is demonstrated that allows for excellent ultrashort pulse generation of an optical communication band. It is therefore anticipated that 2D Se nanosheets may find significant applications in both photoluminescence and ultrafast photonics.In this work, 2D nonlayered selenium nanosheets are fabricated by virtue of the anisotropy of bulk Se itself and probe-sonication liquid-phase exfoliation. The morphology, band gap, optical absorption, crystalline phase, and chemical stability are investigated. Based on these characterizations, the 2D Se nanosheets are realized for ultrafast photonics, and their performance is evaluated.
      PubDate: 2017-11-20T01:53:15.256053-05:
      DOI: 10.1002/adom.201700884
       
  • Through the Spherical Looking-Glass: Asymmetry Enables Multicolored
           Internal Reflection in Cholesteric Liquid Crystal Shells
    • Authors: Yong Geng; Ju-Hyun Jang, Kyung-Gyu Noh, JungHyun Noh, Jan P. F. Lagerwall, Soo-Young Park
      Abstract: Spheres of cholesteric liquid crystal generate dynamic patterns due to selective reflection from a helical structure subject to continuously curved boundaries. So far the patterns are investigated exclusively as function of reflections at the sphere exterior. Here it is shown that the cholesteric shells in a microfluidics produced double emulsion enable also a sequence of internal reflections if the shells have sufficiently thin top and thick bottom. While such asymmetry is promoted by buoyancy when the internal droplet has lower density than the liquid crystal, the elasticity of the cholesteric helix prefers a symmetric shell geometry, acting against gravity. This subtle balance can hide the internal reflections for long time. Eventually, however, the asymmetry is established, revealing a new class of photonic patterns characterized by colored sharp concentric rings. With the complete knowledge of the diverse light-reflecting behavior of cholesteric liquid crystal shells, and utilizing the tunability of the structure period by, e.g., temperature, electric field, or exposure to various chemical species as well as polymer stabilization for making the shells long-term stable, they may be developed into remarkable new optical elements for photonics, sensing, or security pattern generation.Shells of cholesteric liquid crystal can exhibit colorful rings from internal selective reflection. The shell must be thinner at the top than at the bottom, as promoted by buoyancy if the internal liquid has lower density than the liquid crystal. However, such asymmetry is counteracted by the elasticity of the helix, which favors uniform shell thickness.
      PubDate: 2017-11-20T01:52:26.87816-05:0
      DOI: 10.1002/adom.201700923
       
  • Strong Coupling in a Photonic Molecule Formed by Trapping a Microsphere in
           a Microtube Cavity
    • Authors: Jiawei Wang; Yin Yin, Qi Hao, Yang Zhang, Libo Ma, Oliver G. Schmidt
      Abstract: A photonic molecule formed by trapping a microsphere cavity into a hollow microtube cavity is demonstrated, which provides a novel design over conventional photonic molecules comprised of solid-core whispering gallery mode microcavities with externally tangent configuration. Periodic spectral modulations of mode intensity, resonant mode shift, and quality factor are observed owing to the largely mismatched cavity sizes. The intercavity coupling strength can be tuned by shifting the excitation position off the tangent point of the microsphere-tube system along the tube axis, rather than the conventional strategy of changing the spacing between coupled cavities. In particular, anticrossing feature of coupled modes is revealed to verify the existence of optical strong coupling in the microsphere-tube system. Numerical simulation results show an excellent agreement with the experimental observations. The present work provides a flexible strategy for designing photonic molecules and tuning the coupling behavior of resonant modes, which is of high interest for both fundamental and applied studies.A photonic molecule formed by trapping a microsphere into a hollow-core microtube cavity is demonstrated. Whispering gallery mode coupling between two size-mismatched cavities leads to a periodical spectral modulation. The coupling strength can be readily tuned by shifting the excitation position along the tube axial dimension. Mode splitting and anti­crossing feature are observed for inter­actions in the strong coupling regime.
      PubDate: 2017-11-20T01:51:44.028612-05:
      DOI: 10.1002/adom.201700842
       
  • Amplitude Modulation of Anomalously Refracted Terahertz Waves with
           Gated-Graphene Metasurfaces
    • Authors: Teun-Teun Kim; Hyunjun Kim, Mitchell Kenney, Hyun Sung Park, Hyeon-Don Kim, Bumki Min, Shuang Zhang
      Abstract: Although recent progress in metasurfaces has shown great promise for applications, optical properties in metasurfaces are typically fixed by their structural geometry and dimensions. Here, an electrically controllable amplitude of anomalously-refracted waves in a hybrid graphene/metasurface system are experimentally demonstrated, which consists of an artificially constructed two-dimensional metallic apertures array and naturally occurring two-dimensional carbon atoms (graphene) in the subwavelength-scale (< λ/10). Based on Pancharatnam–Berry phase and by careful design of a spatially linear phase profile, it is shown that the amplitude of anomalously refracted circularly cross-polarized terahertz waves can be effectively modulated by an applied gate voltage. The developed electrically tunable graphene metasurfaces may lead to various advanced applications that require dynamical control over electromagnetic waves, such as amplitude tunable active focusing lenses, vortex phase plates and dynamic holography.Electric control of anomalously-refracted waves is demonstrated in a hybrid graphene/metasurface system. Combining two-dimensional apertures based on a concept of Pancharatnam–Berry phase and single-layer graphene, it is shown that the amplitude of anomalously refracted circularly cross-polarized waves can be effectively modulated to a low gate-voltage (< 2.2 V).
      PubDate: 2017-11-20T01:51:16.109801-05:
      DOI: 10.1002/adom.201700507
       
  • Optical Properties of 2D Semiconductor WS2
    • Authors: Chunxiao Cong; Jingzhi Shang, Yanlong Wang, Ting Yu
      Abstract: 2D semiconductor tungsten disulfide (WS2) attracts significant interest in both fundamental physics and many promising applications such as light emitters, photodetectors/sensors, valleytronics, and flexible nanoelectronics, due to its fascinating optical, electronic, and mechanical properties. Herein, basic exciton properties of monolayer WS2 are reviewed including neutral excitons, charged excitons, bounded excitons, biexcitons, and the effects of electrostatic gating, chemical doping, strain, magnetic field, circular polarized light, and substrate on these excitonic structures. Besides basic excitonic emission, single-photon emission, exciton–polaritons, and stimulated emission in monolayer WS2 are also discussed. The understanding of these optical phenomena is critical for the development of potential optical applications in electronic and optoelectronic devices. Finally, a summary and future prospective of the challengers and developments regarding 2D semiconductor WS2 is presented.2D semiconductor WS2 shows promising and significant prospects for future optoelectronics and nanoelectronics. A brief overview of recent advances in the optical properties of monolayer WS2 is provided from the aspects of its basic exciton properties including neutral excitons, charged excitons, bounded excitons, biexcitons, and luminescence beyond basic exciton emission such as single-photon emission, exciton–polaritons, and stimulated emission.
      PubDate: 2017-11-17T07:21:27.446308-05:
      DOI: 10.1002/adom.201700767
       
  • Controllable Photoluminescence Behaviors of Amphiphilic Porphyrin
           Supramolecular Assembly Mediated by Cyclodextrins
    • Authors: Guoxing Liu; Ying-Ming Zhang, Xiufang Xu, Lu Zhang, Qilin Yu, Qian Zhao, Chaoyue Zhao, Yu Liu
      Abstract: Tunable photoluminescence nanomaterials have aroused increasing interest from researchers recently due to their application in bioimaging, photodynamic therapy, and energy conversion. Herein, an artificial ternary nanosystem comprised of dithienylethene-bridged bis(permethyl-β-CD)s, dodecyl-bearing porphyrin, and amphipathic near-infrared (NIR) cyanine fluorochrome is conveniently constructed by rationally designing the host/guest components, dimensions, and properties. In this system, an effective energy transfer (ET) from porphyrin to cyanine fluorochrome leads to the dramatic enhancement of NIR fluorescence intensity and more crucially, this process can be efficiently regulated by distinct light input, achieving photoswitching ET-NIR fluorescence in aqueous media.The energy transfer process from porphyrin to cyanine dye can be reversibly regulated via the photoisomerization of dithienylethene upon light irradiation, thus leading to the photoswitchable near-infrared fluorescence emission in water. The present results provide a feasible supramolecular strategy in designing and constructing versatile light-triggered fluorescence switches for potential application in the fields of biology and materials science.
      PubDate: 2017-11-16T09:46:18.209309-05:
      DOI: 10.1002/adom.201700770
       
  • The First Molecule-Based Blue-Light Optical-Dielectric Switching Material
           in Both Hybrid Bulk Crystal and Flexible Thin Film Forms
    • Authors: Qiang Guo; Wan-Ying Zhang, Qiong Ye, Da-Wei Fu
      Abstract: Three Japanese scientists are awarded the 2014 Nobel Prize in Physics for the invention of a new energy-efficient light source, the blue light-emitting diode, which has great potential in photoelectric applications. However, exploring excellent blue-light materials is still a bigger challenge than red/green ones, especially those with optical-dielectric dual channels of dielectricity and photoluminescence, which are rarely reported and gradually become the main research objects and nodi in the information industry. Herein, the first molecular blue-light switching material, (4-methoxybenzylaminum)2ZnCl4 (1) with many advantages, such as light weight, easy, and environment-friendly processing, controllability, flexibility, and so on, performs optical and dielectric dual switching simultaneously in a single-molecule integrated module. And the multifunctional switching ON/OFF channels can be manipulated in the bulk crystal or unidirectional film by applying an external thermal signal, which shows a high signal-to-noise ratio of 2:1 and a strong fatigue resistance. Besides, the dense film maintains the structural retention characteristic after more than 10 000 times of folding over 90°, which is the mark of its real genius as an ultraflexible blue-light device. This finding will promote the application of blue-light materials in optoelectronic devices and open up a new era of molecule-based blue-light switchable multifunctional materials.The first molecular blue-light optical-dielectric multifunctional switching material, (4-methoxybenzylaminum)2ZnCl4(1), is successfully prepared in both crystal and film forms. It exhibits optical and dielectric dual switching simultaneously with a high signal-to-noise ratio of 2:1 and a strong fatigue resistance upon thermal stimulus. More importantly, it has filled in the blank space in the blue-light multifunctional switching materials.
      PubDate: 2017-11-16T08:30:45.1408-05:00
      DOI: 10.1002/adom.201700743
       
  • Directional Scattering in a Germanium Nanosphere in the Visible Light
           Region
    • Authors: Churong Ma; Jiahao Yan, Yingcong Huang, Guowei Yang
      Abstract: Previous designs of photonic nanoantennas are based on noble metal plasmonic structures, suffering from large ohmic loss and only possessing dipolar plasmon modes. This has driven the intense search for all-dielectric materials (ADMs) beyond noble metals. Here, for the first time, a strong scattering anisotropy in a Ge nanosphere is demonstrated in the visible and near-infrared regions. The forward-to-backward scattering ratio for an individual Ge nanosphere (150 nm) can reach a maximum value of ≈20 theoretically and ≈8 experimentally. This scattering behavior derives from the special real part and imaginary part of refractive index of Ge. Differing form other high-index ADMs such as Si and GaAs, the electric dipole and magnetic dipole resonances of Ge nanospheres are closer to each other in the spectrum due to the non-negligible imaginary part of refractive index. The spectral overlap between electric dipole and magnetic dipole resonances endows Ge nanospheres with efficient directional scattering near the scattering peak. Fano resonances with strong directivity are observed in Ge nanosphere dimers, which is the result of a broad electric gap mode coupled with a hybrid magnetic mode. These findings make Ge nanospheres a promising candidate for nanoantennas, directional sources, and optical switches.The spectral overlap between electric dipole and magnetic dipole resonances derived from non-negligible imaginary part of refractive index endows Ge nanospheres with an efficient directional scattering near the scattering peak.
      PubDate: 2017-11-16T08:27:00.003299-05:
      DOI: 10.1002/adom.201700761
       
  • Enhanced Electroluminescence from ZnO Quantum Dot Light-Emitting Diodes
           via Introducing Al2O3 Retarding Layer and Ag@ZnO Hybrid Nanodots
    • Authors: Liu Yang; Kai Liu, Haiyang Xu, Weizhen Liu, Jiangang Ma, Cen Zhang, Chunyang Liu, Zhongqiang Wang, Guochun Yang, Yichun Liu
      Abstract: Short-wavelength light-emitting diodes (LEDs), a prevalent research topic in modern optoelectronics, have attracted considerable attention in recent years because of their vast application potential in both civil and military domains. Herein, blue-violet LEDs are constructed via a spin-coating solution-processed ZnO quantum dots (QDs) onto p-GaN: Mg wafers. By inserting a thin Al2O3 dielectric retarding layer into the ZnO QDs side, electrons injected from ITO cathode are effectively slowed and detained in the QDs emissive layer, resulting in a ≈30-fold improvement of near-UV electroluminescence intensity from this p-GaN/ZnO QDs/Al2O3/ZnO QDs LED. Furthermore, by replacing pure ZnO QDs with Ag@ZnO hybrid nanodots (synthesized through a simple one-step wet chemical route) as the electron transport layer, the device electroluminescence intensity is further increased. Time-resolved and temperature-dependent spectroscopy reveals that both the spontaneous emission rate and internal quantum efficiency of the ZnO QDs active layer are simultaneously increased as a result of the exciton-localized surface plasmon resonant coupling, which leads to the observed blue-violet electroluminescence enhancement.Blue-violet emission Q-light-emitting diodes (Q-LEDs) are constructed by employing ZnO quantum dots as the active emissive layer. Through introducing an Al2O3 retarding layer and Ag@ZnO hybrid nanodots, the entire electroluminescence intensity of this Q-LED is significantly enhanced. Relevant enhancement mechanisms are attributed to the simultaneous achievement of balanced electron/hole injection and exciton-localized surface plasmon resonant coupling.
      PubDate: 2017-11-16T08:26:24.738212-05:
      DOI: 10.1002/adom.201700493
       
  • Extreme Carrier Depletion and Superlinear Photoconductivity in Ultrathin
           Parallel-Aligned ZnO Nanowire Array Photodetectors Fabricated by
           Infiltration Synthesis
    • Authors: Chang-Yong Nam; Aaron Stein
      Abstract: Ultrathin semiconductor nanowires enable high-performance chemical sensors and photodetectors, but their synthesis and device integration by standard complementary metal-oxide-semiconductor (CMOS)-compatible processes remain persistent challenges. This work demonstrates fully CMOS-compatible synthesis and integration of parallel-aligned polycrystalline ZnO nanowire arrays into ultraviolet photodetectors via infiltration synthesis, material hybridization technique derived from atomic layer deposition. The nanowire photodetector features unique, high device performances originating from extreme charge carrier depletion, achieving photoconductive on–off ratios of>6 decades, blindness to visible light, and ultralow dark currents as low as 1 fA, the lowest reported for nanostructure-based photoconductive photodetectors. Surprisingly, the low dark current is invariant with increasing number of nanowires and the photodetector shows unusual superlinear photoconductivity, observed for the first time in nanowires, leading to increasing detector responsivity and other parameters for higher incident light powers. Temperature-dependent carrier concentration and mobility reveal the photoelectrochemical-thermionic emission process at grain boundaries, responsible for the observed unique photodetector performances and superlinear photoconductivity. The results elucidate fundamental processes responsible for photogain in polycrystalline nanostructures, providing useful guidelines for developing nanostructure-based detectors and sensors. The developed fully CMOS-compatible nanowire synthesis and device fabrication methods also have potentials for scalable integration of nanowire sensor devices and circuitries.Infiltration synthesis enables fully complementary metal-oxide-semiconductor (CMOS)-compatible synthesis of parallel-aligned polycrystalline ZnO nanowire arrays and their integration into ultrasensitive UV detectors featuring ≈1 fA dark currents, the lowest reported for photoconductive photodetectors. The full carrier depletion and photoelectrochemical thermionic emission enable dark currents invariant with increasing number of nanowires,>106 on–off ratios, and unique superlinear photoconductivity, a behavior first observed in nanowires.
      PubDate: 2017-11-15T13:40:50.286805-05:
      DOI: 10.1002/adom.201700807
       
  • Flexible and Adaptable Light-Emitting Coatings for Arbitrary Metal
           Surfaces based on Optical Tamm Mode Coupling
    • Authors: Alberto Jiménez-Solano; Juan F. Galisteo-López, Hernán Míguez
      Abstract: This study demonstrates a design that maximizes the power radiated into free space from a monolayer of nanoemitters embedded in a flexible distributed Bragg reflector conformably attached to a metal surface. This is achieved by positioning the light source at the precise depth within the multilayer for which optical Tamm states provide enhanced quantum yield and outcoupling efficiency, which are combined to optimize the luminous power radiated by the surface of the ensemble. This approach, based on the adhesion of flexible multilayer stacks onto metal surfaces with an arbitrary curvature, is versatile and permits the realization of spectrally narrow monodirectional or self-focusing light-emitting surfaces.A design that maximizes the power radiated into free space from a monolayer of nanoemitters via optical Tamm states is demonstrated. This is achieved by a conformal attachment of a self-standing distributed Bragg reflector embedding the nanoemitters to a metal surface.
      PubDate: 2017-11-15T05:30:48.494231-05:
      DOI: 10.1002/adom.201700560
       
  • Pure Organic Emitter with Simultaneous Thermally Activated Delayed
           Fluorescence and Room-Temperature Phosphorescence: Thermal-Controlled
           Triplet Recycling Channels
    • Authors: Ling Yu; Zhongbin Wu, Cheng Zhong, Guohua Xie, Zece Zhu, Dongge Ma, Chuluo Yang
      Abstract: A new route to utilize the triplet excitons by simultaneous thermally activated delayed fluorescence (TADF) and phosphorescence is demonstrated for a new quinoxaline/phenoxazine hybrid emitter. Moreover, the two triplet recycling channels are thermally controlled, and a clear threshold temperature of 170 K is observed. Below the threshold temperature, direct triplet radiation (phosphorescence) is the dominant process. In contrast, the channel of upconversion through intersystem crossing is activated above the threshold and the resulting TADF gradually becomes the predominant process. By using the new compound as emitter in organic light-emitting diodes, a high external quantum efficiency of 16.8% is far beyond the theoretical limit of the traditional fluorescent emitters.A new quinoxaline/phenoxazine hybrid emitter simultaneously exhibits thermally activated delayed fluorescence and room-temperature phosphorescence. The two triplet recycling channels are thermally controlled with a clear threshold temperature of 170 K.
      PubDate: 2017-11-13T06:30:54.56158-05:0
      DOI: 10.1002/adom.201700588
       
  • Plasmonic Metalens for Narrowband Dual-Focus Imaging
    • Authors: Calum Williams; Yunuen Montelongo, Timothy D. Wilkinson
      Abstract: A new type of metalens with the capability to selectively focus narrowband light is reported at different focal planes depending on polarization. Two zone planes with two different focal lengths are spatially multiplexed and encoded in the subwavelength regime with arrays of orthogonal silver nanostructures, which are designed to exhibit strong wavelength- and polarization-dependent scattering profiles. Using this principle, imaging under white-light illumination with independent focal planes is experimentally demonstrated for each polarization at the narrowband resonant wavelength. Furthermore, each focal plane can be dynamically controlled with an output polarizer. In contrast to conventional refractive and diffractive optical elements, functional metalenses allow additional control over wavelength and polarization properties of light for a wide range of applications.A plasmonic metalens, which selectively focuses narrowband light at different focal planes depending on polarization is demonstrated. Arrays of orthogonal anisotropic silver nanostructures exhibiting strong wavelength- and polarization-dependent scattering profiles are used to encode two different focal length zone plates. The metalens is used to image under white-light illumination and two independent focal planes, for each polarization, at the narrowband resonant wavelength are achieved.
      PubDate: 2017-11-06T06:06:54.915033-05:
      DOI: 10.1002/adom.201700811
       
  • Two-Photon Optical Properties in Individual Organic–Inorganic
           Perovskite Microplates
    • Authors: Qi Wei; Bin Du, Bo Wu, Jia Guo, Ming jie Li, Jianhui Fu, Zhipeng Zhang, Jianwei Yu, Tianyu Hou, Guichuan Xing, Tze Chien Sum, Wei Huang
      Abstract: Metal-halide perovskites are recently extensively investigated as light absorbing material in solar cells. The outstanding optoelectronic properties and tunable light emission of the perovskites also make them promising candidates for light emitting diodes and lasers. However, understanding the relevant mechanisms and processes of the dependence of perovskite light emission on temperature and crystal size is still challenging. Herein, the CH3NH3PbBr3 monocrystals of different sizes are uniformly excited by two-photon absorption at 800 nm (100 fs, 1 KHz). In contrast to the reported relative large exciton binding energy (≈76 meV) and spectrum clearly resolved excitonic absorption, the light emission origin in CH3NH3PbBr3 microcrystals at room temperature is unambiguously determined to be dominated by free electron–hole bimolecular recombination. The coherent light emission threshold of CH3NH3PbBr3 microcrystal increases with temperature, which is closely related to the temperature induced transition from exciton gas to free charge carriers. In addition, the coherent light emission threshold is found to decrease with the microcrystal size, which could be well interpreted by the interaction between the optical confinement, defect density, and cavity quantum electrodynamics effect. These results presented here may facilitate the development of perovskite light emitting diodes and lasers.Photogenerated species and their contributions to lasing performance in MAPbBr3 microplates are investigated. The light emission origin at room temperature is unambiguously determined to be dominated by free-carrier recombination. The lasing threshold decreases with the microcrystal size under two-photon homogeneous excitation, which could be well interpreted by the interaction between the surface charge trapping and cavity- quantum electrodynamics effect.
      PubDate: 2017-11-06T06:03:11.026103-05:
      DOI: 10.1002/adom.201700809
       
  • Realization of Full Control of a Terahertz Wave Using Flexible
           Metasurfaces
    • Authors: Lei Zhang; Min Zhang, Huawei Liang
      Abstract: Compared with devices controlling microwave and visible light, there is a lack of functional devices for terahertz (THz) wave control. Moreover, the available THz elements are usually manufactured with bulk materials, in contrast to the trend of miniaturization and compact device requirements. Here, full control of both phase and amplitude is achieved experimentally and numerically at 0.14 THz, one of the atmospheric windows, by demonstrating the functionalities such as polarization conversion, metalenses and the generation of a non-diffraction Airy beam. Significantly, the metal structures are fabricated on a flexible substrate with a total thickness of ≈0.063 l via a standard flexible printed circuit technique. Taking into account the considerable manipulation efficiency and cost-efficient sample fabrication technique, the results show solid advances in the development of metasurfaces as a versatile platform for designing practical functional devices in the THz range.Both power-efficient and cost-efficient full control of a terahertz wave is realized using flexible metasurfaces. Samples are easily fabricated via a flexible-printed-circuit (FPC) technique on a 100-µm thick plastic polyimide substrate. Polarization conversion, metalens focusing, and generation of an Airy beam are demonstrated to verify the capability of the flexible metasurfaces.
      PubDate: 2017-11-02T08:01:12.930657-05:
      DOI: 10.1002/adom.201700486
       
  • D–A–A-Type Emitter Featuring Benzo[c][1,2,5]thiadiazole and Polar CN
           Bond as Tandem Acceptor for High-Performance Near-Infrared Organic
           Light-Emitting Diodes
    • Authors: Ya-Kun Wang; Sheng-Fan Wu, Si-Hua Li, Yi Yuan, Fu-Peng Wu, Sarvendra Kumar, Zuo-Quan Jiang, Man-Keung Fung, Liang-Sheng Liao
      Abstract: Though urgently required, high performance near-infrared (NIR) emitters are still rare given the challenge of obtaining high photoluminance quantum efficiency (PLQY) at the same time ensuring NIR emission. The major issue lies in the design strategy for which strong electron donating/withdrawing moieties with high PLQY should be integrated with a scrumptious way. Herein, a novel donor–acceptor–acceptor (D–A–A) type NIR emitter comprising highly polar cyano group (CN) together with rigid benzo[c][1,2,5]thiadiazole as tandem acceptor and 4,4′-dimethyltriphenylamine as donor is successfully designed. This constructing strategy not only allows the D/A maintain their intrinsic electron-donating/withdrawing characteristics, but also retains high PLQY. In merits of these features, excellent external quantum efficiency (EQE) of 3.8% with peak emission at 692 nm for 15% doped device is achieved. Encouragingly, impressive EQE of 3.1% with the peak emission at 708 nm is also successfully achieved without doping technique. It is believed that these efficiencies are the best or among the best comparing to those of the reported NIR organic light-emitting diodes with similar electroluminescence peak. Notably, efficiency roll-offs of both doped and nondoped device are also quite flat.D–A–A type near-infrared emitter comprising high polar cyano group (CN) together with benzo[c][1,2,5]thiadiazole as tandem acceptor and 4,4′-dimethyltriphenylamine as donor is successfully achieved. In merits of the scrumptious design strategy, excellent external quantum efficiency (EQE) of 3.8% with peak emission at 692 nm for 15% doped device and EQE of 3.1% peaking at 708 nm are successfully achieved.
      PubDate: 2017-11-02T03:06:31.723814-05:
      DOI: 10.1002/adom.201700566
       
  • High Performances for Solution-Pocessed 0D–0D Heterojunction
           Phototransistors
    • Authors: Yu Yu; Yating Zhang, Xiaoxian Song, Haiting Zhang, Mingxuan Cao, Yongli Che, Haitao Dai, Junnbo Yang, Heng Zhang, Jianquan Yao
      Abstract: All-inorganic cesium lead halide perovskite nanocrystals have emerged as attractive optoelectronic nanomaterials due to their stabilities and highly efficient photoluminescence. High-sensitivity photodetection covering a large spectral range from ultraviolet to near-infrared is dominated by phototransistors. To overcome existing limitations in sensitivity and cost of state-of-the-art systems, new-style device structures and composite material systems are needed with low-cost fabrication and high performance. Here, field-effect phototransistors (FEpTs) based on CsPbBr3–PbS colloidal quantum dot heterostructure dominate to obtain a wide response spectral range and high performance. The large spectral detection spectrum is from 400 to 1500 nm similar to PbS quantum dots' response. It is worth mentioning that the device shows responsivity up to 4.5 × 105 A W−1, which is three orders of magnitude higher than the counterpart of individual material-based devices. Furthermore, other high performance of hybrid CsPbBr3–PbS FEpTs including a short photoresponse time (less than 10 ms) is ascribed to the assistance of heterojunction on the transfer of photoexcitons. The solution-based fabrication process and excellent device performance strongly underscore CsPbBr3–PbS quantum dot as a promising material for future photoelectronic applications.Field effect phototransistors based on CsPbBr3 perovskite-PbS colloidal quantum dot heterostructures dominate to obtain a wide response spectral range and high performance fabricated through a low-cost, solution-processed strategy. These results indicate that solution-based processed perovskite-PbS colloidal quantum dots heterostructures have great potential applications for ultrabroadband photodetection, especially in the infrared (IR) region.
      PubDate: 2017-10-25T10:09:52.232057-05:
      DOI: 10.1002/adom.201700565
       
  • Strong Polarized Photoluminescence from Stretched
           Perovskite-Nanocrystal-Embedded Polymer Composite Films
    • Authors: Wen-Gao Lu; Xian-Gang Wu, Sheng Huang, Lei Wang, Qingchao Zhou, Bingsuo Zou, Haizheng Zhong, Yongtian Wang
      Abstract: Polarized light is very necessary to achieve functional optical systems for display, imaging, and information storage. Luminescent materials with polarized emission are of great interest to achieve polarized light. Here, strong polarized photoluminescence from stretched perovskite-nanocrystal-embedded polymer composite films is reported by combining an in situ fabrication process with controllable mechanical stretching. The material characterizations show that perovskite quantum dots (QDs) in stretched composite films are oriented aligned into wires along the stretching direction. The optical measurements illustrate that the stretched composite films exhibit not only isotropic absorption but also polarized photoluminescence emission. This feature can be explained with their unique structure of “QD-aligned wires”. The achieved polarization ratio is consistent with the calculated results by considering the dielectric confinement of optical electric field and exciton–exciton interactions. In addition, the optimized stretched composite films show strong photoluminescence emission with a polarization ratio of up to 0.33 and a quantum yield of 80%. The use of these composite films in liquid crystal display backlights has potential to increase the light transmittance of polarizers from 50% (without considering the optical loss) to 65%, which is of great significance to improve the energy efficiency.Perovskite nanocrystal-embedded polymer composite films, which exhibit not only isotropic absorption but also strong polarized photoluminescence (PL) are fabricated by combining an in situ method and controllable mechanical stretching. The stretched composite films contain “quantum-dot-aligned wires” along the stretching direction in the polymeric matrix. The polarized PL can be explained by the dielectric confinement effect and exciton–exciton interactions.
      PubDate: 2017-10-25T10:09:38.329917-05:
      DOI: 10.1002/adom.201700594
       
  • Utilizing HomoFRET to Extend DNA-Scaffolded Photonic Networks and Increase
           Light-Harvesting Capability
    • Authors: William P. Klein; Sebastián A. Díaz, Susan Buckhout-White, Joseph S. Melinger, Paul D. Cunningham, Ellen R. Goldman, Mario G. Ancona, Wan Kuang, Igor L. Medintz
      Abstract: DNA-based photonic wires that exploit Förster resonance energy transfer (FRET) between pendant fluorophores to direct and focus excitonic energy have high research interest due to their potential applications in light harvesting, biocomputing, and biosensing. One important goal with these structures is to increase their ability to harvest energy and then transfer it over multiple steps both across extended portions of the spectra and physical space. Toward these goals, incorporating extended homogeneous or homoFRET sections into three unique FRET cascade DNA dendrimer architectures are explored. The effects of inserting increasingly longer homoFRET modules into assemblies based on AF488Cy3Cy3.5Cy5Cy5.5 dye-displaying four-arm, eight-arm, and 2:1 dendrimeric DNA photonic wires are evaluated to understand what these hybrid structures may offer toward increased efficiency. Each structure incorporates an extendable Cy3 homoFRET region capable of incorporating one to six Cy3 repeats. Steady-state and time-resolved fluorescence measurements along with detailed analysis and simulations reveal that despite their modest relay capabilities, the structures are capable of acting as efficient antennas, with the dendrimeric structure manifesting a remarkably high sixfold gain. Moreover, an energy transfer efficiency of ≈3% is possible over nine sequential FRET steps.One important goal of DNA-based photonic wires is increasing their energy harvesting and transfer capacity over multiple steps across extended portions of the spectra. Here, homoFRET sections are incorporated into DNA dendrimers. These structures transfer energy over a remarkable nine sequential Förster resonance energy transfer (FRET) steps acting as efficient antennas with the dendrimers manifesting a sixfold gain.
      PubDate: 2017-10-24T11:41:06.983148-05:
      DOI: 10.1002/adom.201700679
       
  • Plasmonic Polarization-Rotating Emitters with Metallic Nanogroove Antennas
    • Authors: Chengwei Sun; Hongyun Li, Qihuang Gong, Jianjun Chen
      Abstract: A subwavelength plasmonic polarization-rotating emitter is numerically and experimentally demonstrated by designing a metallic nanogroove antenna on the metal surface. The numerical simulation shows that there is a strong resonance in the nanogroove antenna when a surface plasmon polariton mode impinges it, and the polarization of the free-radiation field emitted by the nanogroove antenna is mainly perpendicular to the long side of the nanogroove antenna. As a result, the polarization of the free-radiation field can be easily rotated by tilting the nanogroove antenna. Experimentally, the metallic nanogroove antennas are fabricated, and the polarization-rotating emitters are demonstrated. By tilting the nanogroove antenna with an angle of θ (
      PubDate: 2017-10-23T01:18:16.616615-05:
      DOI: 10.1002/adom.201700510
       
  • High-Efficiency All-Dielectric Metalenses for Mid-Infrared Imaging
    • Authors: Haijie Zuo; Duk-Yong Choi, Xin Gai, Pan Ma, Lei Xu, Dragomir N. Neshev, Baoping Zhang, Barry Luther-Davies
      Abstract: Metasurfaces-based flat optics, which can make use of existing foundry planar technology for high-throughput production, allows the arbitrary control of the wavefront and polarization of light within subwavelength thick structures. So far, however, flat optics for the mid-infrared (MIR) has received far less attention than devices operating at visible or near-infrared wavelengths. Here, polarization-insensitive, highly efficient, all-dielectric metalenses operating in the MIR around 4 µm are demonstrated. The metalens is designed using rigorous coupled-wave analysis and is based on hydrogenated amorphous silicon (α-Si:H) nanopillars supported by an MgF2 substrate. The metalenses produce close to a diffraction-limited focal spot and can resolve structures on the wavelength scale where the focusing efficiency reaches 78% at a magnification of 120×. The imaging qualities are comparable with commercial bulk-molded chalcogenide aspheric lenses. These results provide novel solutions for existing MIR technology and nurture new functionalities with the population of miniaturized and planarized optoelectrical devices.Polarization-insensitive, highly efficient, all-dielectric metalenses operating in mid-infrared are demonstrated. The metalens is designed using rigorous coupled-wave analysis, realized with amorphous silicon nanopillars on MgF2 substrate. The devices produce close to a diffraction-limited focal spot and are comparable with commercial lenses in imaging quality. These results provide novel solutions for infrared technology and nurture new functionalities in miniaturized, planarized photonic devices.
      PubDate: 2017-10-23T01:16:17.580607-05:
      DOI: 10.1002/adom.201700585
       
  • Gold Nanobipyramid-Enhanced Hydrogen Sensing with Plasmon Red Shifts
           Reaching ≈140 nm at 2 vol% Hydrogen Concentration
    • Authors: Hang Kuen Yip; Xingzhong Zhu, Xiaolu Zhuo, Ruibin Jiang, Zhi Yang, Jianfang Wang
      Abstract: Plasmonic sensors that make use of localized surface plasmon resonance provide an excellent platform for hydrogen sensing. In this work, large plasmonic red shifts are obtained on (Au nanobipyramid core)@(Pd shell) bimetallic nanostructures for hydrogen sensing. Au nanobipyramid@Pd nanostructures with different shell thicknesses are synthesized by varying the Pd precursor amount. The Au nanobipyramid@Pd nanostructures with thicker Pd shells are found to exhibit larger responses to hydrogen. The maximal plasmonic red shift reaches 97 nm at 4 vol% hydrogen concentration. The shell morphology of the Au nanobipyramid@Pd nanostructures is further optimized to improve the hydrogen sensing performance. With the optimized nanostructures, the maximal plasmonic red shift is improved to ≈140 nm at 2 vol% hydrogen concentration. Compared with the Au nanobipyramid@Pd nanostructures, Au nanobipyramid/AgPd nanostructures show smaller plasmonic red shifts under the same conditions. The highly enhanced plasmonic shifts and sensitivity to hydrogen make our Au nanobipyramid@Pd nanostructures highly promising for the development of optical hydrogen sensing devices.Bimetallic Au–Pd nanostructures based on Au nanobipyramids are synthesized for hydrogen sensing. Both the thickness and morphology of the Pd shell deposited on Au nanobipyramids are optimized. An unprecedented sensitivity to hydrogen is achieved, where the red plasmon shifts upon the exposure to 2 and 4 vol% hydrogen reach 140 and 147 nm, respectively.
      PubDate: 2017-10-23T01:11:55.898063-05:
      DOI: 10.1002/adom.201700740
       
  • MoS2 for Ultrafast All-Optical Switching and Modulation of THz Fano
           Metaphotonic Devices
    • Authors: Yogesh Kumar Srivastava; Apoorva Chaturvedi, Manukumara Manjappa, Abhishek Kumar, Govind Dayal, Christian Kloc, Ranjan Singh
      Abstract: In recent years, the stunning performance of transition metal dichalcogenides (TMDCs) has been utilized in the area of field effect transistors, integrated circuits, photodetectors, light generation and harvesting, valleytronics, and van der Waals (vdW) heterostructures. However, the optoelectronic application of TMDCs in realizing efficient, ultrafast metaphotonic devices in the terahertz part of the electromagnetic spectrum has remained unexplored. The most studied member of the TMDC family, i.e., MoS2, shows an ultrafast carrier relaxation after photoexcitation with near-infrared femtosecond pulse of energy above the bandgap. Here, this study investigates the photoactive properties of MoS2 to demonstrate an ultrasensitive active switching and modulation of the sharp Fano resonances in MoS2-coated metamaterials consisting of asymmetric split ring resonator arrays. The results show that all-optical switching and modulation of micrometer scale subwavelength Fano resonators can be achieved on a timescale of hundred picoseconds at moderate excitation pump fluences. The precise and active control of the MoS2-based hybrid metaphotonic devices open up opportunities for the real-world technologies and realization of ultrafast switchable sensors, modulators, filters, and nonlinear devices.Photoactive properties of MoS2 thin film enable low fluence modulation of Fano resonance in a hybrid MoS2-metamaterial device. The drop casting of MoS2 turns out to be a robust and facile method to integrate MoS2 with subwavelength photonic metadevices and manifest the ultrafast switching of Fano resonances at picosecond time scale.
      PubDate: 2017-10-23T01:11:20.7559-05:00
      DOI: 10.1002/adom.201700762
       
  • Microengineering of Optical Properties of GeO2 Glass by Ultrafast Laser
           Nanostructuring
    • Authors: Fangteng Zhang; Ausra Cerkauskaite, Rokas Drevinskas, Peter G. Kazansky, Jianrong Qiu
      Abstract: Nanostructuring in glass by ultrafast laser paves the way for integrated optics. In this paper, form birefringence induced by ultrafast laser direct writing in GeO2 glass is systematically investigated. It is shown that the pulse energy for maximum retardance in GeO2 glass is ≈65% lower than in fused silica. The induced retardance by laser scanning is two times higher than that by stationary irradiation under the same processing conditions. The optimum pulse duration for maximum retardance in GeO2 glass lies within sub-picosecond region, i.e., typically around 500 fs, while in fused silica it is in the picosecond regime at around 1–2 ps. A reversed polarization dependence of retardance at low pulse densities and low pulse repetition rates is observed in GeO2 glass. As a result, two optical applications including a radial polarization vortex converter and a computer-generated hologram are demonstrated in GeO2 glass by spatial manipulation of the optical axis of the locally induced form birefringence. The microengineering of optical properties of GeO2 glass by ultrafast laser direct writing may lead to new applications in near-/mid-infrared optics.Ultrafast laser direct-write nanostructuring of GeO2 glass leads to the formation of local form birefringence with a polarization-dependent optical slow axis. Manipulation of the retardance value and the orientation of the local optical axis of the induced-form birefringence enables fabrication of various optical elements with continuous phase profiles such as radial polarization vortex converters and computer-generated holograms.
      PubDate: 2017-10-18T01:01:23.706484-05:
      DOI: 10.1002/adom.201700342
       
  • Periodic Dielectric Metasurfaces with High-Efficiency, Multiwavelength
           Functionalities
    • Authors: David Sell; Jianji Yang, Sage Doshay, Jonathan A. Fan
      Abstract: Metasurfaces are thin-film optical devices for tailoring the phase fronts of light. The extension of metasurfaces to multiple wavelengths has remained a major challenge, and existing design techniques do not yield devices with high efficiency. This study reports a new design method, based on inverse freeform optimization, that enables high-efficiency, multiwavelength metasurfaces. Using an iterative optimization solver, this study incorporates multiple wavelength responses into wavelength-scale design domains in a straightforward and automated manner. In principle, this method can readily scale to a very large number of wavelengths. As a proof of concept, this study designs and characterizes periodic transmissive metasurfaces, made from silicon, that deflect N different incident near-infrared wavelengths to N unique diffraction orders. The theoretical and experimental efficiencies of these devices scale as 1/N0.5, which is significantly better than current state-of-the-art devices. The implementation of large-angle, broadband blazed grating devices is also demonstrated. This study envisions that this inverse design method can generalize to high-performance, multiwavelength, aperiodic devices, and that it serves as a potential route to broadband metasurfaces.An inverse optimization design method that can produce high-efficiency, multiwavelength metasurfaces is reported. As a proof of concept, periodic transmissive metasurfaces made from silicon are designed and characterized. These devices deflect N different incident near-infrared wavelengths to N unique diffraction orders, and their absolute efficiencies scale as 1/N0.5, which is significantly better than current state-of-the-art devices.
      PubDate: 2017-10-16T01:36:38.185152-05:
      DOI: 10.1002/adom.201700645
       
  • Improving the Power Efficiency of Solution-Processed Phosphorescent WOLEDs
           with a Self-Host Blue Iridium Dendrimer
    • Authors: Shumeng Wang; Qingqing Yang, Baohua Zhang, Lei Zhao, Debin Xia, Junqiao Ding, Zhiyuan Xie, Lixiang Wang
      Abstract: Solution-processed phosphorescent white organic light-emitting diodes (WOLEDs) with improved power efficiency are reported by simply blending a yellow phosphor Ir(Flpy-CF3)3 into a self-host blue Ir dendrimer B-G2. Attributable to the elimination of the host-induced power efficiency losses existed in the traditional host-based devices, a state-of-the-art total power efficiency as high as 48.8–62.8 lm W−1 is achieved at a practical luminance of 1000 cd m−2. Moreover, without considerably sacrificing the power efficiency, the related correlated color temperature and Commission Internationale de L'Eclairage coordinates can be well tuned to satisfy different illumination requirements. The results clearly demonstrate that the adoption of a self-host blue phosphorescent dendrimer instead of the traditional host-based device structure is a superior and promising strategy to realize power-efficient white-light emitting devices.Solution-processed phosphorescent white organic light-emitting diodes (WOLEDs) with improved power efficiency are reported by simply blending a yellow phosphor Ir(Flpy-CF3)3 into a self-host blue iridium dendrimer B-G2. Attributable to the elimination of the host-induced power efficiency losses existing in the traditional host-based devices, a state-of-the-art total power efficiency as high as 48.8–62.8 lm W–1 is achieved at 1000 cd m–2.
      PubDate: 2017-10-16T01:35:38.448606-05:
      DOI: 10.1002/adom.201700514
       
  • The Next-Generation of Nonlinear Optical Materials:
           Rb3Ba3Li2Al4B6O20F—Synthesis, Characterization, and Crystal Growth
    • Authors: Hongwei Yu; Joshua Young, Hongping Wu, Weiguo Zhang, James M. Rondinelli, Shiv Halasyamani
      Abstract: Nonlinear optical (NLO) materials are of intense academic and technological interest attributable to their ability to generate coherent radiation over a range of different wavelengths. The requirements for a viable NLO material are rather strict, and their discovery has mainly been serendipitous. This study reports synthesis, characterization, and, most importantly, growth of large single crystals of a technologically viable NLO material—Rb3Ba3Li2Al4B6O20F. Through the judicious selection of cations, Rb3Ba3Li2Al4B6O20F exhibits a 3D structure that facilitates the growth of large single crystals along the optical axis direction. Measurements on these crystals indicate that Rb3Ba3Li2Al4B6O20F exhibits a moderate birefringence of 0.057 at 1064 nm enabling Type I phase-matching down to 243 nm. Theoretical calculations indicate the symmetry adapted mode displacement (SAMD) parameter scales with the second-harmonic generation intensity.A next-generation technologically viable nonlinear optical crystal, Rb3Ba3Li2Al4B6O20F, is successfully designed, synthesized, characterized, and grown. This crystal not only solves the layering issue observed in KBe2BO3F and Sr2Be2B2O7, which has hindered their crystal growth, but also does not require the use of toxic BeO in the synthesis. More importantly, it exhibits a moderate birefringence and is nonhygroscopic.
      PubDate: 2017-10-10T04:35:45.926227-05:
      DOI: 10.1002/adom.201700840
       
  • Molecular-Printed Thermochromic with Fast Color Switching
    • Authors: Sungjun Cho; Gwangmook Kim, Sooun Lee, Jinwoo Park, Wooyoung Shim
      Abstract: Color generation by thermochromic materials offers several advantages over the light-based technology: a passive circuit element-driven simplified device layout, cost-effectiveness, and clear visibility. However, thermochromic materials need to be effectively coupled with an external heat source to induce coloration, which generally involves slow heat transfer processes that are not suitable for potential display applications. Here, a method for molecular printing of a thermochromic ink with a low heat capacity, enabling an unprecedented, fast color switching without any optoelectronic elements, is demonstrated. Molecularly printed ink is patterned on fabricated microheaters that induce transient local heat generation, facilitating local heating and cooling processes. Depending on the density of the thermochromic ink, that is, the number of microcapsuled dyes in the form of a monolayer resulting in a low heat capacity, the chroma of the patterned ink could be increased. Using this technique, the thermochromic ink could be printed over centimeter scales, with cyan-magenta-yellow-black colors at a color-switching rate of 20–500 ms, to be integrated into the thermochromic device prototype for potential display applications.A molecular-printed thermochromic reflective color display that can generate fast color switching is realized by printing monolayerd thermochromic ink. To induce color switching, local heating is used to activate the printed ink on a resistive heater array. This architecture is not only simple and scalable, but also addresses the color switching limitations of chromic displays via reducing the heat capacity.
      PubDate: 2017-10-10T00:22:21.958883-05:
      DOI: 10.1002/adom.201700627
       
  • Bioinspired Anti-Moiré Random Grids via Patterning Foams
    • Authors: Zheng Li; Zhandong Huang, Qiang Yang, Meng Su, Xue Zhou, Huizeng Li, Lihong Li, Fengyu Li, Yanlin Song
      Abstract: Transparent conductors with specific patterns are essential for touch screens as sensing electrodes. Among them, metal grids are a kind of optimal alternative for traditional transparent conductors, while moiré patterns hinder metal grids in the application of display planes. Nevertheless, random or aperiodic pattern grids can avoid the patterns. A series of bioinspired random (BR) grids is demonstrated that can avoid moiré patterns and exhibit great optoelectronic performance comparable to indium tin oxide (ITO). The BR grids comprising random hexagons originate from biological networks with line arrangements that are random and aperiodic. They are fabricated through a controllable and highly efficient method of patterning foams, and are composed of close-packed silver nanoparticles (AgNPs). This type of grid has potential to extend applications of high-transparent functional devices.Anti-moiré random grids with irregular hexagons inspired by the networks of veins in a dragonfly's wings are easily fabricated using a patterning foams method. The proposed method can quickly assemble silver nanoparticles into a variety of complicated random grids. Experiments show that the as-fabricated grids can effectively avoid Moiré patterns compared to regular grids. These anti-moiré grids hold promise for applications in liquid crystal displays.
      PubDate: 2017-10-10T00:21:18.97497-05:0
      DOI: 10.1002/adom.201700751
       
  • Broadband Surface-Enhanced Photoluminescence Based on Gold Nanocubic
           Self-Assembly
    • Authors: Yufeng Ding; Yunchang You, Yungang Sang, Yanrong Wang, Man Zhao, Chao Liang, Chenguang Lu, Dahe Liu, Jing Zhou, Zhiyong Tang, Jinwei Shi
      Abstract: Low-cost materials with large-area, broadband, and strong photoluminescence are of great interest in many fields. Plasmonic enhancement structures, based on nanoparticle self-assembly, are identified as promising candidates for achieving these requirements. This study fabricates Au nanocube assemblies and demonstrates photoluminescence enhancement of quantum dots (QDs) deposited on their surfaces. The enhancement factor of this large-area ensemble is ≈3.5 with the use of a 532 nm pulse laser to excite red-emissive QDs. Furthermore, the broadband response of this assembly is studied and enhanced broadband white-light emission is found. Finally, a new optical information storage method based on this photoluminescence enhancement is demonstrated. The results have significance for applications, such as energy-saving lighting and displays, solar energy harvesting, optical data storage, and anticounterfeiting measures.Plasmonic nanoparticle self-assembly is identified as one of the most promising techniques to achieve large-area, broadband, and low-cost strong photoluminescence. This study demonstrates that Au nanocubic self-assembly can have an obvious and broadband photoluminescence enhancement effect for quantum dots with different colors. This technique has great potential applications, such as enhanced RGB white-light emission, optical storage, and anticounterfeiting.
      PubDate: 2017-10-09T01:20:46.284779-05:
      DOI: 10.1002/adom.201700551
       
  • Supramolecular Synthesis of Multifunctional Holey Carbon Nitride Nanosheet
           with High-Efficiency Photocatalytic Performance
    • Authors: Shipeng Wan; Man Ou, Qin Zhong, Shule Zhang, Wei Cai
      Abstract: Novel carbon nitride (CN) nanosheets are for the first time fabricated by facial supramolecular approach using cyanuric acid, melamine, and 2,4-diamino-6-methyl-1,3,5-triazine as starting materials. This is also the first report where the third monomer is used in such synthetic route. With the unique structural advantages for efficient separation of photoinduced charge–hole pairs, light absorption, and the richly available restive sites, the as-synthesized porous CN nanosheets exhibit a superior photocatalytic hydrogen evolution activity whether they are under simulated solar light or under visible light (λ> 420 nm) irradiation. The hydrogen evolution rate can reach 11 946.1 µmol h−1 g−1 under visible light irradiation, to the best of our knowledge, the highest of all the metal-free CN semiconductor photocatalysts. Also, the synthetic holey CN nanosheets exhibit excellent photocatalytic oxidation performance of high concentration nitric oxide (NO, ≈400 ppm) and outstanding photocatalytic degradation of rhodamine B under visible light. The supramolecular synthesis of multifunctional CN nanosheets using suitable monomers as raw materials may provide a possible pathway for alleviating energy issues and environmental pollution problems.Multifunctional carbon nitride nanosheets are successfully synthesized using a supramolecular approach. They exhibit excellent photocatalytic performances on water splitting to H2, oxidation of nitric oxide, and degradation of rhodamine B. Particularly inspiring is that the hydrogen evolution rates can reach 11 946.1 µmol g−1 h−1 under visible light. The outstanding photocatalytic performances are due to the synthetic carbon nitride nanosheets' intrinsic properties.
      PubDate: 2017-10-06T08:56:10.856705-05:
      DOI: 10.1002/adom.201700536
       
  • Polymeric P–N Heterointerface for Solution-Processed Integrated
           Organic Optoelectronic Systems
    • Authors: Jihong Kim; Dongyoon Khim, Jun-Seok Yeo, Minji Kang, Kang-Jun Baeg, Dong-Yu Kim
      Abstract: Conventionally, P–N junctions have played an important role as a key unit in most semiconductor electronic devices. P–N junctions based on organic semiconductors have also been researched widely, but it is difficult to develop solution-processing-based organic semiconductor P–N junctions because of their similar solubility in common organic solvents. For this reason, most organic planar heterojunctions have been based on deposition by thermal evaporation or transfer film via additional complicated processing. In this study, using p-type and n-type conjugated polymers with selection of their orthogonal solvents, a conjugated polymer bilayer P–N heterojunction structure is developed via simple solution processing. The developed structure is then used in novel organic electronic applications, such as organic rectifier diodes, organic field-effect transistors with highly balanced ambipolar charge transport properties, integrated circuits, and even organic phototransistors that display a photoresponse from the visible to the near-infrared (NIR) range with the generation of a photocurrent at the P–N heterointerface in the channel region. The polymeric P–N junction structure can be applied in various organic electronic devices via a simple printing process, which can contribute to the development of new functionalized organic electronics systems.Using p- and n-type conjugated polymers and their orthogonal solvents, a polymeric bilayer P–N heterojunction structure is developed via simple solution processing, and it is applied into assorted novel organic-electronic applications. The polymeric P–N heterojunction structure can be combined with a simple printing process, which may widely contribute to develop new functionalized organic-electronic systems via easy processing.
      PubDate: 2017-10-04T11:57:42.183758-05:
      DOI: 10.1002/adom.201700655
       
  • Optically Controlled Magnetization and Magnetoelectric Effect in Organic
           Multiferroic Heterojunction
    • Authors: Mengmeng Wei; Mengsi Niu, Pengqing Bi, Xiaotao Hao, Shenqiang Ren, Shijie Xie, Wei Qin
      Abstract: The organic multiferroic effect receives increasing attention in organic electronics. Recently, the renaissance of organic multiferroics has yielded in a deep understanding of organic magnetism and magnetoelectric coupling. Here, through fabricating polythiophene nanowire/CH3NH3PbBr3 multiferroic heterojunction, the origin of organic magnetism, optically controlled magnetization, and magnetoelectric coupling with optical approach is studied. Specifically, the optical approach utilizes double beam 355 and 607 nm excitations to separately operate the CH3NH3PbBr3 and polythiophene nanowire layers. This double-beam-light approach allows to elucidate the effects of photogenerated charges on organic magnetism and magnetoelectric coupling effect. It is found that magnetization and magnetoelectric coupling of polythiophene nanowire/CH3NH3PbBr3 heterojunction can be effectively tuned through the photoexcitation of CH3NH3PbBr3, rather than photoexcitation of polythiophene nanowire phase, which has been further confirmed by electron spin resonance. Furthermore, the dominated factors are discussed to reveal room-temperature magnetization in organics. This work provides a strategy for optically controlled organic magnetism and magnetoelectric effect in charge transfer heterojunction.In polythiophene nanowire (PT-nw)/CH3NH3PbBr3 heterojunction, under 355 nm light illumination, charge transferring between PT-nw and CH3NH3PbBr3 breaks a closed-shell structure to form an open-shell structure, in which room temperature magnetism can be observed. However, the closed-shell structure is kept when applying 607 nm light illumination. In this case, no magnetism is observed in PT-nw/CH3NH3PbBr3 heterojunction.
      PubDate: 2017-10-04T04:41:06.861161-05:
      DOI: 10.1002/adom.201700644
       
  • 2D TiS2 Layers: A Superior Nonlinear Optical Limiting Material
    • Authors: Sreekanth J. Varma; Jitesh Kumar, Yang Liu, Katherine Layne, Jingjie Wu, Chenglu Liang, Yusuke Nakanishi, Amir Aliyan, Wei Yang, Pulickel M. Ajayan, Jayan Thomas
      Abstract: The advancement in high power lasers has urged the requisite of efficient optical limiting materials for both eye and sensor protection. The discovery of atomically thin 2D transition metal dichacogenides with distinctive properties has paved the way for a variety of applications including optical limiting. Until recently, the optical limiting effect exhibited by 2D materials is inferior to the benchmark materials fullerene (C60) and graphene. This article reports the optical limiting activity of the 2D transition metal dichalcogenide, titanium disulfide (TiS2) nanosheets, using optical and photoacoustic z-scan techniques. The 77% nonlinear optical limiting exhibited by the TiS2 sheets with 73% linear-transmittance is superior to that of any other existing 2D dichalcogenide sheets, graphene, and the benchmark optical limiting material, C60. The enhanced nonlinear response is attributed to the concerted effect of 2-photon and the induced excited state absorptions. By using photoacoustic z-scan, a unique tool developed to determine the nonlinear optical limiting mechanism in materials, it is found that the optical limiting exhibited by TiS2 2D sheets and graphene are mainly due to nonlinear absorption rather than scattering effects. These results have opened the door for 2D-dichalcogenide-materials-based highly efficient optical limiters, especially at low fluences.2D Dichalcogenide nanosheets are of great demand due to their incredible optical and electrical properties. 2D TiS2 nanosheets prepared by liquid-phase exfoliation exhibit appreciable optical limiting properties and are found to be superior to the benchmark materials such as graphene and C60. Nonlinear optical limiting is a concerted effect of 2-photon absorption and induced excited-state absorption.
      PubDate: 2017-10-04T04:40:47.666871-05:
      DOI: 10.1002/adom.201700713
       
  • Fluorescent Humidity Sensors Based on Photonic Resonators
    • Authors: Katalin Szendrei; Alberto Jiménez-Solano, Gabriel Lozano, Bettina V. Lotsch, Hernán Míguez
      Abstract: Among the different approaches to humidity sensing available, those based on fluorescent signals are gathering a great deal of attention due to their fast response and versatility of detection and design. So far, all proposals have focused on the use of luminescent probes whose emission is either triggered or inhibited by the presence of water that reacts or alters their chemical environment, hence inducing the signal change. Here, a novel concept in fluorescent humidity sensing based on combining stimuli-responsive photonic resonators with molecular fluorescent probes is introduced. The resonator is assembled from humidity-swellable antimony phosphate nanosheets embedding a planar light-emitting probe, whose emission is dramatically modified by the changes that ambient humidity causes in its photonic environment. Guided by “in silico” optical design of the resonator architecture and subsequent experimental realization, two embodiments of fluorescent photonic humidity sensors featuring turn-on and turn-off detection schemes are presented. The interplay between the luminescent properties of an emitter and its photonic environment implies a fundamental advantage as the emitters are not chemically altered during the detection process. At the same time, it paves the way toward a new generation of photonic humidity sensors which can conveniently be interfaced with common fluorescence detection schemes.A novel concept in fluorescent humidity sensing is herein presented by precisely locating a thin light-emitting layer of nanospheres inside a moisture-responsive photonic crystal resonator.
      PubDate: 2017-09-29T12:08:27.835635-05:
      DOI: 10.1002/adom.201700663
       
  • Beam-Editing Coding Metasurfaces Based on Polarization Bit and
           Orbital-Angular-Momentum-Mode Bit
    • Authors: Qian Ma; Chuan Bo Shi, Guo Dong Bai, Tian Yi Chen, Ahsan Noor, Tie Jun Cui
      Abstract: Coding metasurfaces are aimed at representing digital information of the metasurface, usually by programing digital unit cells to control electromagnetic waves. However, some information sequences cannot be recognized by the receiver, because of nonorthogonality of the usual phase codes. Here, new coding method is proposed to encode information with orthogonal parameters in the emitting beam, which reduces information loss in the system. A vector beam modulator is proposed by combining orthogonal polarizations and orbital angular momentum (OAM) modes. A normal incident wave can be modulated by OAM-mode bit and polarization bit, which are regarded as specific information by the receiver. A polarization converter is used to realize the polarization selection (polarization bit) and phase control, independently. The phase patterns on the coding metasurfaces can be programed to realize the designed OAM modes (OAM bits) in the microwave frequency. Three schemes are presented to emit multiple OAM modes in dual polarizations, one of which is manufactured and measured for near and far fields. The simulations and experiments are in outstanding agreement, verifying the excellent performance of the proposed schemes. This work has great potential in communication applications of coding metasurfaces.A new design method is proposed for coding metasurfaces to encode the information with orthogonal polarization bit and orbital angular momentum mode bit in the emitting beam. Compared to most coding metasurfaces presented before, this method can reduce information loss in the system dramatically.
      PubDate: 2017-09-21T01:12:39.649681-05:
      DOI: 10.1002/adom.201700548
       
  • Multifunctional Phenanthroimidazole Derivatives to Realize
           High-Performance Deep-Blue and White Organic Light-Emitting Diodes
    • Authors: Xiaoyang Du; Guang Li, Juewen Zhao, Silu Tao, Caijun Zheng, Hui Lin, Qingxiao Tong, Xiaohong Zhang
      Abstract: Deep blue emitters with high quantum yield, good stability, and multifunctionality are still the key technology for white organic light-emitting diodes (WOLEDs). To address this, two multifunctional deep-blue materials 4-{2-[4′-(1,4,5-triphenyl-4,5-dihydro-1H-imidazol-2-yl)-biphenyl-4-yl]-3a,11b-dihydro-phenanthro[9,10-d]imidazol-1-yl}-benzonitrile (CPD) and 4-(2-{4′-[1-(4-tert-butyl-phenyl)-4,5-diphenyl-4,5-dihydro-1H-imidazol-2-yl]-biphenyl-4-yl}-3a,11b-dihydro-phenanthro[9,10-d]imidazol-1-yl)-benzonitrile (tCPD) based on phenanthroimidazole units are designed, synthesized, and characterized. Both the materials show high quantum yields and good stabilities. The deep-blue fluorescent devices using CPD and tCPD as emitters show maximum external quantum efficiency (EQE) of 5.80% and 4.71% along with Commission Internationale de I'Eclairage (CIE) coordinates of (0.15, 0.07) and (0.15, 0.09), respectively. Two-color based WOLEDs are demonstrated by doping Ir(MDQ)2acac into CPD and tCPD with a low doping concentration, both devices show high EQEs of 16.4% and 16.6% and CIEs of (0.49, 0.34) and (0.48, 0.32), respectively. Furthermore, three-color based fluorescence/phosphorescence-WOLEDs (F/P-WOLEDs), with reasonable exciton management, are fabricated to enhance exciton utilization and improve device performance. CPD-based WOLED shows high efficiencies of 49.4 cd A−1, 53.5 lm W−1, 19.0%, and CIE coordinate of (0.46, 0.46). With the same structure, tCPD-based device also shows high efficiencies of 40.6 cd A−1, 47.2 lm W−1, 19.4% along with CIE coordinate of (0.43, 0.45). These results are among the best of reported deep-blue OLEDs and F/P-WOLEDs.Two novel multifunctional phenanthroimidazole derivatives are used to construct high performance white organic light-emitting diodes (WOLEDs). Step-wise energy transfer takes place to enhance exciton utilization and improve device performance. As a consequence, high external quantum efficiency of over 19% and power efficiency of over 50 lm W−1 with stable electroluminescence spectra are achieved for WOLEDs.
      PubDate: 2017-09-14T06:15:58.41987-05:0
      DOI: 10.1002/adom.201700498
       
 
 
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