Numerical analysis of homojunction design for high-efficiency Pb-free perovskite solar cells

Tin-based perovskite solar cells (PSCs) exhibit promising potential as viable alternatives to the prevailing lead-based PSCs, owing to their ideal bandgap and environmentally friendly nature. To address the challenges posed by the thick perovskite films required for narrow bandgap materials, we propose incorporating p-n homojunctions within the active layers. This approach not only enables a charge transport layer (CTL)-free cell structure to reduce manufacturing costs but also enhances the performance of PSCs with CTLs by facilitating efficient charge segregation. We initially emphasize the advantages of CTL-free PSCs and subsequently strive to optimize the performance of homojunction PSCs, encompassing a comprehensive analysis of influential factors such as the absorber layer thickness, doping concentration, defect density, carrier mobility, and electrode contacts. A power conversion efficiency of 19.07% was achieved for the CTL-free homojunction PSCs. Then various charge transport materials were incorporated to further enhance the performance of homojunction PSCs. Ultimately, a champion power conversion efficiency of 25.15% was achieved for the PSCs with CTLs. The present investigation contributes to the advancement of solar cell technology by shedding light on the potential of lead-free PSCs, as well as optimizing their performance for real-world applications.