Abstract

This work presents a comparative numerical investigation of ZnO/CIGS/Cu₂O and ZnO/CIS/Cu₂O heterojunction thin-film solar cells using the one-dimensional SCAPS-1D simulation software. The study aims to evaluate and compare the influence of three key parameters: absorber thickness, acceptor doping concentration, and operating temperature on the photovoltaic performance of both device architectures. The effects of these parameters on the open-circuit voltage (Voc), short-circuit current density (Jsc), fill factor (FF), and power conversion efficiency (PCE) were systematically analyzed. The simulation results show that increasing the absorber thickness initially enhances device performance by improving light absorption and carrier generation, whereas excessive thickness promotes bulk recombination, leading to reductions in Voc and PCE. Likewise, moderate acceptor doping strengthens the built-in electric field and improves Voc and FF, while excessive doping induces severe recombination losses, particularly in the CIS-based device, resulting in significant performance degradation. Furthermore, increasing the operating temperature causes a marked decrease in Voc, FF, and PCE, whereas Jsc exhibits only a slight increase due to the temperature-induced narrowing of the absorber bandgap. A comparative analysis reveals that at a temperature of 300 K, the CIS absorber delivers a higher Jsc of 44.075 mA·cm⁻² owing to its lower bandgap, whereas the CIGS absorber consistently achieves higher Voc, FF, and PCE of 0.735 V, 81.06%, and 25.13%, respectively, together with better thermal and electrical stability. Overall, the results demonstrate that the performance of chalcopyrite heterojunction solar cells is governed by the combined optimization of absorber thickness, acceptor doping concentration, and operating temperature. These findings provide valuable insights for the design and optimization of high-efficiency CIGS/CIS thin-film photovoltaic devices.

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