Numerical Simulation Approach for an Investigation of Critical Parameters of ZTO Buffer Layer for CZTS Photovoltaic Cell Performance: A One-Dimensional Modeling

A Kesterite CZTS semiconductor contains earth-abundant elements and has been recognized as a promising absorber layer for highly efficient and low-cost thin-film solar cells. We present a numerical approach for analyzing the performance of CZTS-based photovoltaic cell with a non-toxic ZTO buffer layer through the use of a solar cell capacitance simulator. The performance of the p-CZTS/n-ZTO device has been examined in terms of ZTO buffer layer parameters such as thickness, donor concentration, mid-gap defect density, electron affinity and bandgap. The maximum cell efficiency obtained for the conduction band offset was 0.2 eV, which shows a small spike at the interface between the absorber and the buffer layers. In the optimized cell, the efficiency and fill factor were found to be 17.48% and 82.53%, respectively, which is the highest value reported so far. There are different kinds of current–voltage distortions observed, such as crossover and red-kink behavior, and the reason behind these distortions have been discussed. The results of this study provide valuable insights into the development of Cd-free highly efficient solar cells based on CZTS.