Optical and electronic properties of chemical bath deposited p-CuO and n-ZnO nanowires on silicon substrates: p-CuO/n-ZnO nanowires solar cells with high open-circuit voltage and short-circuit current

Abstract

P-type cupric oxide (p-CuO) and p-type cupric-oxide/n-type zinc oxide nanowires (p-CuO/n-ZnO NWs) heterojunction diodes were fabricated by employing chemical bath deposition technique on n-silicon (n-Si) substrate. The work demonstrates the potential of zinc oxide nanowires as window layer owing to its wide and direct band gap for metal oxide based solar cells. Optical and electronic properties of the CuO film and ZnO nanowires including refractive index, absorption coefficient and band gaps were investigated by using spectroscopic ellipsometric analysis. Impact of nanowire morphology, chemical composition and crystallite structures on optical and photovoltaic performance of p-CuO/n-Si and p-CuO/n-ZnO NWs were investigated. Absorption coefficient in the near UV–visible range was observed to improve significantly by incorporating n-ZnO nanowires which was desired for the solar cell applications. The comparative photovoltaic performance showed improvements of both the short-circuit current density (Jsc) and open circuit voltage (Voc), due to reduced interface recombination and enhanced absorption for the increased surface-to-volume ratio of ZnO nanowires in the p-CuO/n-ZnO NWs heterojunction. Photovoltaic performance with Jsc, Voc and power conversion efficiency of 11.1 mA/cm2, 1.1 V and 4.19% was obtained. Therefore, the work emphasizes importance of using the combination of n-ZnO nanowires and p-CuO film as the wide- and low- band gap materials for improving performance of the future low-cost solar cell with superior efficiency.