Performance analysis of tungsten disulfide (WS2) as an alternative buffer layer for CdTe solar cell through numerical modeling

Abstract

Abstract The cadmium telluride (CdTe) solar cells are the most widely used high efficiency thin film solar cells that have shown stable performance over a long time. Although being a frontier in thin film technology, the performance of CdTe solar cells is setback by pinhole effects when thin CdS buffer layers are used in devices for compensating the spectral loss. To overcome this, generally, a highly resistive ZnO is used as window layer between the transparent conducting oxide (TCO) and the CdS layer. In this work, a single tungsten disulfide (WS2) is proposed to replace the bilayer window in conventional CdTe solar cells. The band discontinuities at two interfaces of the WS2 in the proposed structure (p-CdTe/n-WS2/n-ITO) are studied with varying defect state density. The performance parameters such as open circuit voltage, short circuit current, fill factor, and efficiency are observed respectively for different defect state densities of interfaces and the bulk layer of WS2. Comparison between the conventional CdTe structure and proposed structure shows that the CdTe solar cells with a single WS2 buffer layer can perform as efficiently as the one with CdS/ZnO bilayer.