Device Engineering and Performance Optimization of Cu2NiGeS4 Thin-Film Solar Cells with In2S3/MoTe2 Charge-Selective Layers: A Computational Study
The pursuit of efficient and sustainable thin-film photovoltaics increasingly demands absorber materials that combine strong optical absorption with earth-abundant and environmentally benign constituents. Cu2NiGeS4 (CNGS) has emerged as a promising quaternary chalcogenide absorber owing to its favorable optoelectronic properties and high absorption coefficient, yet its photovoltaic potential remains comparatively underexplored, particularly in conjunction with optimized charge-selective layers. Here, we introduce and comprehensively investigate an CNGS-based solar-cell architecture using SCAPS-1D, with In2S3 and MoTe2 serving as the electron and hole-transport layers respectively. The analysis of energy-band profiles, electric fields, carrier distributions, and generation-recombination characteristics reveals the mechanisms governing carrier separation and extraction across the heterojunctions. Systematic optimization of layer thickness, doping density, bulk and interface defect densities, recombination coefficients, parasitic resistances, temperature, and illumination intensity identifies the key factors limiting device performance. The optimized device is predicted to achieve a power conversion efficiency (PCE) of 28.44% with a open-circuit voltage (VOC) of 0.984 V, short-circuit current density (JSC) of 34.39 mA/cm2, and fill factor (FF) of 84.04%, under AM1.5G illumination at 300 K. This simulated efficiency exceeds the previously reported 6.25-21.17% range for CNGS-based solar cells considered in this study. The findings establish In2S3/CNGS/MoTe2 as a promising platform for next-generation thin-film photovoltaics and provide physically grounded design guidelines for absorber optimization, interface engineering, and future experimental realization.