Numerical simulation and performance optimization of all-inorganic CsGeI₃ perovskite solar cells with stacked ETLs/C₆₀ by SCAPS device simulation

Perovskite solar cells, particularly those featuring CsGeI3 as the absorption layer, are distinguished by their nontoxicity and inherent stability. In this work, to optimize the interface contact of the cells, enhance their built-in electric field, and consequently augment the power conversion efficiency, a C60 layer was incorporated into the electronic transport layer. This incorporation led to the formation of a novel dual-electron transport layer structure. Employing SCAPS-1D simulation software, a range of electron and hole transport layer combinations was explored. The optimal configuration was determined to be FTO/SnO2/C60/IDL1/CsGeI3/IDL2/Cu2O/Au. The absorption layer's thickness, doping concentration, defect density, and bandgap were optimized. Furthermore, an investigation was conducted on the performance implications arising from alterations in the dual electron conduction layer SnO2/C60's thickness, bandgap, and doping concentration. Concurrently, adjustments were made to refine the defect density in the interface defect layer, and an investigation was carried out to determine the optimal operational temperature. These endeavors culminated in the achievement of an impressive 30.34% optimal power conversion efficiency, representing a significant 54.25% enhancement over the preoptimization efficiency of 19.67%. This work stands as a valuable reference for subsequent investigations into the dual electron transport layer structure in Ge-based perovskite solar cells.