A numerical approach to study the effect of bandgap and electron affinity in HTL-free perovskite solar cells and design of two-terminal silicon/ perovskite tandem solar cell

The hole-transport layer (HTL) free perovskite solar cells with carbon electrode (c-PSCs) have garnered significant attention owing to their simple design, cost-effectiveness, and good stability. However, the power conversion efficiency (PCE) of these cells is still very low in comparison to conventional PSCs that utilize HTLs and metal electrodes. Tandem solar cells (TSCs) based on perovskite and crystalline silicon (c-Si) solar cells are considered possible contenders for surpassing the theoretical maximum limit and addressing the efficiency constraints encountered in single junction PSCs. The current research work assesses the design and optimization of a c-Si/c-PSC-based two-terminal (2-T) monolithically coupled TSC utilizing a one-dimensional solar cell capacitance simulator (SCAPS-1D) software. Initially, a detailed examination of standalone c-PSC has been conducted to evaluate bandgap and electron affinity variation. Then, the optimized c-PSC was integrated with the bottom c-Si cell by adopting a widely employed current matching technique. An investigation was undertaken to identify a current matching condition between two subcells that yielded optimal performance for the device. Under optimum conditions, a Voc of 2.138 V, Jsc of 15.60 mA/cm2, FF of 85.79%, and PCE of 28.62% were achieved in a 2-T monolithically connected tandem cell. We believe the results acquired in this study would be of significant importance in advancing highly efficient 2-T tandem cells based on HTL-free c-PSCs.