Issue 13, 2020

Enhancement in the performance of nanostructured CuO–ZnO solar cells by band alignment

Abstract

In this study, we investigated the effect of cobalt doping on band alignment and the performance of nanostructured ZnO/CuO heterojunction solar cells. ZnO nanorods and CuO nanostructures were fabricated by a low-temperature and cost-effective chemical bath deposition technique. The band offsets between Zn1−xCoxO (x = 0, 0.05, 0.10, 0.15, and 0.20) and CuO nanostructures were estimated using X-ray photoelectron spectroscopy and it was observed that the reduction of the conduction band offset with CuO. This also results in an enhancement in the open-circuit voltage. It was demonstrated that an optimal amount of cobalt doping could effectively passivate the ZnO related defects, resulting in a suitable conduction band offset, suppressing interface recombination, and enhancing conductivity and mobility. The capacitance–voltage analysis demonstrated the effectiveness of cobalt doping on enhancing the depletion width and built-in potential. Through impedance spectroscopy analysis, it was shown that recombination resistance increased up to 10% cobalt doping, thus decreased charge recombination at the interface. Further, it was demonstrated that the insertion of a thin layer of molybdenum oxide (MoO3) between the active layer (CuO) and the gold electrode hinders the formation of a Schottky junction and improved charge extraction at the interface. The ZnO/CuO solar cells with 10% cobalt doped ZnO and 20 nm thick MoO3 buffer layer achieved the best power conversion efficiency of 2.11%. Our results demonstrate the crucial role of the band alignment on the performance of the ZnO/CuO heterojunction solar cells and could pave the way for further progress on improving conversion efficiency in oxide-based heterojunction solar cells.

Graphical abstract: Enhancement in the performance of nanostructured CuO–ZnO solar cells by band alignment

  • This article is part of the themed collection: Solar energy

Supplementary files

Article information

Article type
Paper
Submitted
21 dec 2019
Accepted
14 feb 2020
First published
24 feb 2020
This article is Open Access
Creative Commons BY-NC license

RSC Adv., 2020,10, 7839-7854

Enhancement in the performance of nanostructured CuO–ZnO solar cells by band alignment

A. Kaphle, E. Echeverria, D. N. Mcllroy and P. Hari, RSC Adv., 2020, 10, 7839 DOI: 10.1039/C9RA10771A

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