Toward High-Efficiency CIGS-based Thin-film Solar Cells Incorporating Surface Defects Layer, through a Comparative Study of Electrical Characteristics-SCAPS 1D Modeling

This research contribution investigates a way of improving performance of CIGSe-based second-generation thin-film solar cells by analyzing output parameters of two reference cells using cadmium sulfide and zinc sulfide as buffer layers. The performances are improved by acknowledging both the exceptional properties of ZnS as a buffer layer, and the beneficial contributions of an indium-enrich layer, which form a surface defect layer at the ZnS/CIGSe heterojunction. SCAPS-1D numerical modeling software is used to conduct calculations, and the structure using ZnS enables achieving an efficiency of 24.31%. Deeper investigation on the effects of variation of functional layers properties such as bandgap, electron affinity, doping level, and thickness enables retaining an optimized structure, and results show an improved efficiency of 25.22% and a fill factor of 80.26%, indicating of a fluid flow of charge carriers, thus a more stable device. All simulations are performed considering experimental environment parameters, an external temperature of 300 K, light illumination of AM1.5G, and defects states are assumed in both the bulk and at interfaces.

Automated summary

This research investigates a method to improve the performance of CIGSe-based thin-film solar cells by analyzing the output parameters of two reference cells with different buffer layers. The use of ZnS as a buffer layer and an indium-enriched layer at the ZnS/CIGSe heterojunction results in improved performance. Numerical modeling software is used to calculate the efficiency, and the ZnS structure achieves an efficiency of 24.31%. Further analysis of functional layer properties leads to an optimized structure, resulting in improved efficiency of 25.22% and a stable flow of charge carriers.