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ACS Appl Mater Interfaces. 2018 Nov 7;10(44):38264-38271. doi: 10.1021/acsami.8b14408. Epub 2018 Oct 19.

Consecutive Junction-Induced Efficient Charge Separation Mechanisms for High-Performance MoS2/Quantum Dot Phototransistors.

Author information

1
Department of Engineering Science , University of Oxford , Parks Road , Oxford OX1 3PJ , United Kingdom.
2
Department of Energy Systems , Soonchunhyang University , Asan 31538 , Chungcheongnam-do , Republic of Korea.
3
Department of Information and Communication Engineering , Daegu Gyeongbuk Institute of Science and Technology (DGIST) , Daegu 711-873 , Republic of Korea.
4
Division of Physics and Semiconductor Science , Dongguk University , Seoul 04620 , Republic of Korea.
5
Department of Physics , Sungkyunkwan University , Suwon 16419 , Gyeonggi-do , Republic of Korea.
6
Electrical Engineering Division, Department of Engineering , University of Cambridge , 9 JJ Thomson Avenue , Cambridge CB3 0FA , United Kingdom.

Abstract

Phototransistors that are based on a hybrid vertical heterojunction structure of two-dimensional (2D)/quantum dots (QDs) have recently attracted attention as a promising device architecture for enhancing the quantum efficiency of photodetectors. However, to optimize the device structure to allow for more efficient charge separation and transfer to the electrodes, a better understanding of the photophysical mechanisms that take place in these architectures is required. Here, we employ a novel concept involving the modulation of the built-in potential within the QD layers for creating a new hybrid MoS2/PbS QDs phototransistor with consecutive type II junctions. The effects of the built-in potential across the depletion region near the type II junction interface in the QD layers are found to improve the photoresponse as well as decrease the response times to 950 μs, which is the faster response time (by orders of magnitude) than that recorded for previously reported 2D/QD phototransistors. Also, by implementing an electric-field modulation of the MoS2 channel, our experimental results reveal that the detectivity can be as large as 1 × 1011 jones. This work demonstrates an important pathway toward designing hybrid phototransistors and mixed-dimensional van der Waals heterostructures.

KEYWORDS:

built-in potential; fast photodetectors; hybrid phototransistors; lead sulfide quantum dots; molybdenum disulfide

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