Bandgap engineering and high-throughput defect dynamics in two-terminal CsGeI₃-Si monolithic tandem solar cells

Simulation-driven investigations are presented on highly efficient monolithic tandem solar cells with climate-efficient nano-scaled perovskite and crystalline silicon for green energy generation. Tandem solar cells comprise a lead-free CsGeI₃ perovskite top cell and a silicon bottom sub-cell. A Cu₂O hole transport material layer and a ZnO electron transport material layer was used. Optimizations were performed by varying doping, defect concentration, thickness, and band gap to obtain valuable insights into material properties. These perovskite-silicon tandem solar cells, with a wide band gap and optimized parameters, yielded power conversion efficiencies above the Shockley-Queisser limit for single-junction cells. The structure of perovskite-silicon tandem solar cells is Glass/FTO/ZnO/CsGeI₃/Cu₂O/RL/Si(p⁺)/Si(p)/Si(n)/Au. After optimization, the results show a power conversion efficiency of 37.23%, a J_sc of 23.95 mA/cm², a Voc of 1.895 V, and an FF of 82%. This research shows that through this hybrid perovskite-silicon technology, one is assured of increased energy output while decreasing carbon footprints and increasing renewable energy use.