Spectroscopic Ellipsometry Analysis and EQE Simulation of CIGS Solar Cell to Optimize CdS/ZnO Interface Layer.

Dhurba R. Sapkota, Manoj K. Jamarkattel, Rabee B. Alkhayat Wright Center for Photovoltaics Innovation and Commercialization, University of Toledo, Toledo, OH, United States

A thin-film of  copper indium gallium diselenide, Cu (In, Ga)Se2  also known as CIGS has been deposited on Mo coated soda lime glass by thermal co-evaporation of Cu, In, Ga, and Se sources. CIGS film has identified as a p-type by characterizing it with energy-dispersive X-ray spectroscopy (EDS) and its thickness is estimated ∽1.2 µm by spectroscopic ellipsometry analysis. The device has been completed with the successive deposition of SLG/Mo/CIGS/CdS/ZnO/ITO and ∽ 11% efficiency is obtained from EQE measurement. Spectroscopic ellipsometry measurement and analysis of device has been performed.  External quantum efficiency (EQE) simulation is then performed by using the final layer stack obtained by SE analysis. Impact of CdS/ZnO interface layer on device performance is studied. It is observed that thinner the CdS/ZnO layer, higher the efficiency.