|TITLE||Continuous color-tunable light-emitting devices based on compositionally graded monolayer transition metal dichalcogenide alloys|
|AUTHOR||Jiang Pu*, Hao Ou, Tomoyuki Yamada, Naoki Wada, Hibiki Naito, Hiroto Ogura, Takahiko Endo, Zheng Liu, Toshifumi Irisawa, Kazuhiro Yanagi, Yusuke Nakanishi, Yanlin Gao, Mina Maruyama, Susumu Okada, Keisuke Shinokita, Kazunari Matsuda, Yasumitsu Miyata*, and Taishi Takenobu|
The diverse series of transition metal dichalcogenide (TMDC) materials has been employed in various optoelectronic applications, such as photodetectors, light-emitting diodes, and lasers. Typically, the detection or emission range of optoelectronic devices is unique to the bandgap of the active material. Therefore, to improve the capability of these devices, extensive efforts have been devoted to tune the bandgap, such as gating, strain, and dielectric engineering. However, the controllability of these methods is severely limited (typically ~0.1 eV). In contrast, alloying TMDCs is an effective approach that yields a composition-dependent bandgap and enables light emissions over a wide range. In this study, we fabricated a color-tunable light-emitting device using compositionally graded TMDC alloys. The monolayer WS2/WSe2 alloy grown by chemical vapor deposition showed a spatial gradient in the light emission energy, which varied from 2.1 to 1.7 eV. We incorporated this alloy in an electrolyte-based light-emitting device structure that can tune the recombination zone laterally. Thus, we successfully fabricated a continuous and reversible color- tunable light-emitting device by controlling the light-emitting positions. Our results provide a new approach for exploring monolayer semiconductor-based broadband optical applications.
|KEYWORDS||Light-emitting devices, Transition metal dichalcogenides, Alloys, Ion gels, EL|