Enhancement in the performance of nanostructured CuO–ZnO solar cells by band alignment. Issue 13 (24th February 2020)

• Record Type: Journal Article
• Authors: Kaphle, Amrit; Echeverria, Elena; Mcllroy, David N.; Hari, Parameswar
• Is Part Of: RSC advances. Volume 10:Issue 13(2020)
• Page Start: 7839
• Page End: 7854
• Publication Date: 2020-02-24
• Subjects: Chemistry -- Periodicals; 540.5
• DOI: 10.1039/c9ra10771a
• Languages: English
• ISSNs: 2046-2069

Abstract

Abstract : Nanostructured ZnO/CuO photovoltaic cell with power conversion efficiency of 2.11%. 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− x Co x O ( 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.