3rd TAGRA

Interface defects in perovskite solar cells (PSCs) are recognized as a major source of non-radiative recombination, which adversely affects device performance. In this study, the impact of interface defect density on the performance of a lead-free FTO/TiO₂/KSnI₃/Cu₂O/Au perovskite solar cell was investigated using the SCAPS-1D simulation platform. The simulation model was initially validated against a previously reported device, yielding a power conversion efficiency (PCE) of 8.87%, which closely matches the reported value of 8.88%. To evaluate the influence of interface defects, the defect densities at the TiO₂/KSnI₃ and KSnI₃/Cu₂O interfaces were independently varied from 10¹⁰ to 10²⁰ cm⁻³. The results revealed a pronounced difference in defect sensitivity between the two interfaces. Increasing the defect density at the TiO₂/KSnI₃ interface led to substantial reductions in open-circuit voltage (Voc) and overall efficiency, whereas the KSnI₃/Cu₂O interface exhibited relatively stable performance across a broader defect-density range. The optimum defect densities were identified as 1 × 10¹⁰ cm⁻³ for the TiO₂/KSnI₃ interface and 1 × 10¹⁴ cm⁻³ for the KSnI₃/Cu₂O interface. Under these optimized conditions, the device achieved a Voc of 1.1679 V, Jsc of 15.34 mA cm⁻², FF of 79.49%, and PCE of 14.24%, representing an efficiency enhancement of approximately 60% compared with the reference device. As all other device parameters were kept constant throughout the study, the observed improvement can be attributed solely to the reduction of interface-assisted recombination losses. These findings indicate that the TiO₂/KSnI₃ interface is the primary recombination pathway in the device and underscore the critical role of ETL/absorber interface engineering in improving the performance of lead-free KSnI₃ perovskite solar cells.