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

Abstract

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.