Impact of improvements in ZnO thin film solution process on ZnO/Cu2O solar cell performance

Abstract

ZnO semiconductor is an ideal n-type window material for a solar cell owing to both the abundance of zinc in nature and its stable structure. The preparation of ZnO thin films with proper crystallinity is still possible only with expensive production methods. It is challenging to grow high quality ZnO thin film by the sol-gel spin coating method which is simple and low-cost. Generally, ZnO thin films prepared by spin coating method demonstrate poor crystallinity properties. The crystallinity of ZnO and hence the heterojunction efficiency can be enhanced, by simply improving the solution process. Additionally, the comparison of solar cell efficiency based on the quality of ZnO thin film prepared by the spin coating method in the literature is still a deficiency. Therefore, in this study, the semiconductor properties of ZnO thin films prepared by a spin coating method using the improved solution process compared to our previous study were investigated. The p-Cu 2 O thin film electrodeposition was achieved by our novel low-cost two-electrode cell utilizing a simple DC power supply and microammeter. The semiconductor properties of ZnO thin films and their impacts on ZnO/Cu 2 O bilayer heterojunction efficiency were elaborated by means of structural, optoelectronic, and I–V characterizations. The crystal quality of ZnO has been significantly improved, and a large increase in the output current and voltage of the fabricated solar cells has been achieved. • The preparation of ZnO thin films with proper crystallinity require expensive vacuum based equipment. • It is challenging to grow high quality ZnO thin film by sol-gel spin coating method which is simple and low cost. • By simply improving the solution process, the ZnO/Cu 2 O solar cell output voltage and current can be enhanced. • Investigation of various combination of ZnO/Cu 2 O based heterostructures.