Photodetection in p–n junctions formed by electrolyte-gated transistors of two-dimensional crystals

Daichi Kozawa, Jiang Pu, Ryo Shimizu, Shota Kimura, Ming-Hui Chiu, Keiichiro Matsuki, Yoshifumi Wada, Tomo Sakanoue, Yoshihiro Iwasa, Lain-Jong Li, Taishi Takenobu

Research output: Contribution to journalArticlepeer-review

16 Scopus citations

Abstract

Transition metal dichalcogenide monolayers have attracted much attention due to their strong light absorption and excellent electronic properties. These advantages make this type of two-dimensional crystal a promising one for optoelectronic device applications. In the case of photoelectric conversion devices such as photodetectors and photovoltaic cells, p–n junctions are one of the most important devices. Here, we demonstrate photodetection with WSe2 monolayer films. We prepare the electrolyte-gated ambipolar transistors and electrostatic p–n junctions are formed by the electrolyte-gating technique at 270 K. These p-n junctions are cooled down to fix the ion motion (and p-n junctions) and we observed the reasonable photocurrent spectra without the external bias, indicating the formation of p-n junctions. Very interestingly, two-terminal devices exhibit higher photoresponsivity than that of three-terminal ones, suggesting the formation of highly balanced anion and cation layers. The maximum photoresponsivity reaches 5 mA/W in resonance with the first excitonic peak. Our technique provides important evidence for optoelectronics in atomically thin crystals.
Original languageEnglish (US)
Pages (from-to)201107
JournalApplied Physics Letters
Volume109
Issue number20
DOIs
StatePublished - Nov 16 2016

Bibliographical note

KAUST Repository Item: Exported on 2020-10-01
Acknowledgements: D.K. acknowledges the support of the Grant-in-Aid for Encouragement of Young Scientists (B) (JSPS KAKENHI Grant No. JP 16K17485) from Japan Society for the Promotion of Science (JSPS). Y.W., J.P., and K.M. acknowledge the Leading Graduate Program in Science and Engineering, Waseda University, from JSPS. D.K. and J.P. were supported by the Grant-in-Aid for JSPS Fellows (JSPS KAKENHI Grant Nos. JP 15J07423 and JP 14J07485). T.S. is grateful to the Grant-in-Aid for Encouragement of Young Scientists (A) (JSPS KAKENHI Grant No. JP 26706012) from JSPS. T.T. was partially supported by the Funding Program for the Next Generation of World-Leading Researchers from JSPS, and Grants-in-Aid from MEXT (JSPS KAKENHI Grant Nos. JP 16K13618, JP 26102012 “π-System Figuration,” and JP 25000003 “Specially Promoted Research”).

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