Role of a Solution-Processed VO Hole Extracting Layer on the Performance of CuO-ZnO-Based Solar Cells.

In this research, a heterostructure of the CuO-ZnO-based solar cells has been fabricated using low-cost, earth-abundant, non-toxic metal oxides by a low-cost, low-temperature spin coating technique. The device based on CuO-ZnO without a hole transport layer (HTL) suffers from poor power conversion efficiency due to carrier recombination on the surface of CuO and bad ohmic contact between the metal electrode and the CuO absorber layer. The main focus of this research is to minimize the mentioned shortcomings by a novel idea of introducing a solution-processed vanadium pentoxide (VO) HTL in the heterostructure of the CuO-ZnO-based solar cells. A simple and low-cost spin coating technique has been investigated to deposit VO onto the absorber layer of the solar cell. The influence of the VO HTL on the performance of CuO-ZnO-based solar cells has been investigated. The photovoltaic parameters of the CuO-ZnO-based solar cells were dramatically enhanced after insertion of the VO HTL. VO was found to enhance the open-circuit voltage of the CuO-ZnO-based solar cells up to 231 mV. A detailed study on the effect of defect properties of the CuO absorber layer on the device performance was theoretically accomplished to provide future guidelines for the performance enhancement of the CuO-ZnO-based solar cells. The experimental results indicate that solution-processed VO could be a promising HTL for the low-cost, environment-friendly CuO-ZnO-based solar cells.