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Adv Mater. 2018 Dec;30(49):e1804020. doi: 10.1002/adma.201804020. Epub 2018 Oct 1.

Graphene/Organic Semiconductor Heterojunction Phototransistors with Broadband and Bi-directional Photoresponse.

Author information

1
School of Optoelectronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu, 610054, P. R. China.
2
School of Optoelectronic Science and Engineering, University of Electronic Science and Technology of China, State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 610054, P. R. China.
3
School of Microelectronics, Xidian University, Xian, 710071, P. R. China.
4
National Laboratory of Solid State Microstructures, School of Electronic Science and Engineering, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, P. R. China.

Abstract

A graphene-semiconductor heterojunction is very attractive for realizing highly sensitive phototransistors due to the strong absorption of the semiconductor layer and the fast charge transport in the graphene. However, the photoresponse is usually limited to a narrow spectral range determined by the bandgap of the semiconductor. Here, an organic heterojunction (C60 /pentacene) is incorporated on graphene to realize a broadband (405-1550 nm) phototransistor with a high gain of 5.2 × 105 and a response time down to 275 µs. The visible and near-infrared parts of the photoresponsivity (9127 A W-1 @650 nm and 1800 A W-1 @808 nm) come from the absorption of the organic layer and the graphene, respectively. For the first time, a bi-directional (positive and negative) photoresponse is demonstrated at different wavelengths, due to the opposite charge transfer direction of the photoexcited carriers enforced by the unique band alignment. Such tunability will enable new functionalities such as large-scale real-time optical image and infrared focal plane array detection in the future.

KEYWORDS:

bi-directional response; broadband detection; graphene/organic heterojunctions; high gain; phototransistors

PMID:
30276886
DOI:
10.1002/adma.201804020

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