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18. Electrically Tunable Excitonic Light Emitting Diodes based on Monolayer WSe2 p-n Junctions

Author

Ross, Jason S., Klement, Philip, Jones, Aaron M., Ghimire, Nirmal J., Yan, Jiaqiang, Mandrus, D. G., Taniguchi, Takashi, Watanabe, Kenji, Kitamura, Kenji, Yao, Wang, Cobden, David H, and Xu, Xiaodong

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Materials Science
Abstract

Light-emitting diodes are of importance for lighting, displays, optical interconnects, logic and sensors. Hence the development of new systems that allow improvements in their efficiency, spectral properties, compactness and integrability could have significant ramifications. Monolayer transition metal dichalcogenides have recently emerged as interesting candidates for optoelectronic applications due to their unique optical properties. Electroluminescence has already been observed from monolayer MoS2 devices. However, the electroluminescence efficiency was low and the linewidth broad due both to the poor optical quality of MoS2 and to ineffective contacts. Here, we report electroluminescence from lateral p-n junctions in monolayer WSe2 induced electrostatically using a thin boron nitride support as a dielectric layer with multiple metal gates beneath. This structure allows effective injection of electrons and holes, and combined with the high optical quality of WSe2 it yields bright electroluminescence with 1000 times smaller injection current and 10 times smaller linewidth than in MoS2. Furthermore, by increasing the injection bias we can tune the electroluminescence between regimes of impurity-bound, charged, and neutral excitons. This system has the required ingredients for new kinds of optoelectronic devices such as spin- and valley-polarized light-emitting diodes, on-chip lasers, and two-dimensional electro-optic modulators., Comment: 13 pages main text with 4 figures + 4 pages upplemental materials

Published
2013
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40. Isolation and characterization of blackish-brown BY2-melanin accumulated in cultured tobacco BY-2 cells

Author

Islam, Abul Taher Mohammed Rafiqul, Shinzato, Keita, Miyaoka, Hiroki, Komaguchi, Kenji, Koike, Kanae, Arakawa, Kenji, Kitamura, Kenji, and Tanaka, Nobukazu

Abstract

The tobacco BY-2 cell line is one of the most utilized plant cell lines. After long-term culture, the cells turn brown to black, but the causal pigment is unknown. We successfully isolated a blackish-brown pigment from BY-2 cells cultured for 3 weeks. Morphological and spectroscopic analyses indicated that the pigment had similar features to a melanin-like substance reported previously. Furthermore, physicochemical analyses revealed that this pigment possessed most of the properties of melanin-like pigments. In addition, the high nitrogen content suggested that it differed from common plant melanins classified as allomelanins, suggesting a novel eumelanin-like pigment: “BY2-melanin”. This is the first example showing that eumelanin-like pigments are produced in the cultures of plant cells for which the accumulation of melanin has not been reported. This tobacco BY-2 cell culture technique may represent a customizable and sustainable alternative to conventional melanin production platforms, with significant potential for industrial and pharmacological applications.Graphical AbstractMorphological and spectroscopic analyses and physicochemical characterizations revealed that “BY2-melanin” isolated from BY-2 cells was a novel eumelanin-like pigment.

Published
2023
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