Investigation of FeS₂ Thin Film as a Hole Transport Layer in CuAl_1–<i>x</i>Fe_<i>x</i>S₂-Based Solar Cells: A Strategy to Improve Efficiency

To minimize losses due to recombination in solar cells, the incorporation of a hole transport layer (HTL) has emerged as a promising strategy. However, selecting the appropriate HTL for a given absorber material presents several challenges. This study focuses on modeling and optimization of two solar cell configurations utilizing CuAl1–xFexS2 [x = 1 (Cell-1) and 0.75 (Cell-2)] as the absorber material and sputtering deposited FeS2 thin film as the HTL material to enhance their efficiency using the Silvaco ATLAS device simulator. The deposition of FeS2 thin film by direct current sputtering, followed by annealing in a sulfur environment, is also demonstrated. The sulfurized thin films exhibit a p-type conductivity. Following the incorporation of HTL and the optimization of different parameters, both solar cells exhibit significantly increased hole current toward back contact, indicating less recombination and efficient charge extraction. The experimental efficiencies of Cell-1 (3.58%) and Cell-2 (5.29%) improved to 7.28% and 9.80% in the simulation with an optimized structure, showing enhancements of 103% and 85%, respectively.