A Simplified Front-Contact Layer for Reduced Recombination and Improved Performance of (Ag,Cu)(In,Ga)Se2 Solar Cells

Transparent conductive oxide (TCO) layers play a critical role in determining optical transmission, carrier collection, and interfacial recombination in thin-film solar cells. In Cu(In,Ga)Se2 (CIGS) devices, the widely used ZnO/AZO front contact often introduces parasitic optical absorption due to its relatively large thickness. Here, we introduce a front-contact layer (FCL) structure to replace the conventional thick ZnO/AZO stack. Structural and interfacial analyses reveal that the FCLs form a dense, conformal contact, significantly reducing the interface trap density and suppressing recombination losses. The optimized front-contact structure reduces parasitic optical losses and improves device performance from 16.25% to 17.30%, with the most notable gains in VOC and FF, consistent with reduced interfacial recombination. Electrical characterization and optical simulations further indicate reduced saturation current density and improved diode behavior, consistent with enhanced junction quality. Importantly, the reduced thickness and high transparency of the FCLs make this architecture highly suitable for tandem photovoltaic applications, where efficient light management and minimal optical loss are essential.