Article

2020; 20(3): 445-450

Published online January 13, 2020 https://doi.org/10.1016/j.cap.2020.01.006

Copyright © The Korean Physical Society.

Photocurrent spectra for above and below bandgap energies from photovoltaic PbS infrared detectors with graphene transparent electrodes

Kim J., Ampadu E.K., Oh E., Choi H., Ahn H.-Y., Cho S.-H., Choi W.J., Byun J.Y.

Department of Physics, Chungnam National University, Daejeon, South Korea; Electronics and Telecommunications Research Institute, Daejeon, South Korea; Korea Institute of Science and Technology, Seoul, South Korea

Correspondence to:Oh, Eunsoon
Department of Physics, Chungnam National University

Received: December 19, 2019; Accepted: January 6, 2020

Abstract

We discussed photocurrent spectra of photovoltaic PbS infrared detectors using multi-layer graphene as transparent electrode, where p-PbS films were deposited on TiO2/FTO substrates by chemical bath deposition. In the photocurrent spectra, we observed both above-bandgap and sub-bandgap photocurrent without any external bias. We discussed impurity band model and grain boundary model in order to explain the sub-bandgap photocurrent near 15 μm. Since FTO is transparent in the visible range, we were able to illuminate green laser beam from the FTO back-side, and photo-response up to 50 μm was found to be enhanced. This long wavelength photo-response was attributed to the excitation of the photo-electrons accumulated at the TiO2/PbS interface. Our photovoltaic PbS devices can detect not only short-infrared but also terahertz radiation at room temperature, which is highly applicable to various fields. © 2020 Korean Physical Society

Keywords: Infrared detectors, Lead sulfide, Multilayer graphene, Photocurrent spectra, Photovoltaic

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