Optimization of CdS buffer layer for high efficiency CIGS solar cells

초록

CdS thin films are widely used as a buffer layer in CIGS thin film solar cells. There are many methods to fabricate CdS thin films, such as chemical bath deposition (CBD), close spaced sublimation (CSS), metal organic chemical vapor deposition (MOCVD), pulsed-laser deposition, spray pyrolysis, and sputtering. Among them, the CBD technique has been proven to be the most suitable method to produces CdS thin films for photovoltaic applications because it is an efficient, cost-effective, and large-area deposition method. It has been reported that the highest efficiency of 20.3% has been achieved for thin film solar cells based on CIGS utilizing CdS films prepared by the CBD technique. However, the benefits of using CBD-CdS films have been merely observed so far but not completely understood. The aim of this work is to optimize CdS buffer layer for the high efficiency CIGS solar cells by investigating the chemical and electronic properties at the heterointerfaces in the solar cells with those buffers. For this, we studied the formation of the CdS/CIGS interface, focusing on the interaction between the CIGS absorber layer and a standard chemical bath solution for the CdS deposition.