Optimization of all Pb-free perovskite CsGeI3/FASnI3 tandem solar device with 30.42% efficiency: Numerical simulation using SCAPS

Lead-free Hybrid Organic-Inorganic perovskite have gained remarkable interest for photovoltaic application due to their lack of toxicity. In this work, We report the findings obtained from simulation with the SCAPS-1D software of an all Pb-free perovskite solar tandem device. The (CsGeI3) with 1.6 eV band gap is employed as a top-cell, while, the bottom-cell is FASnI3 with a band gap of 1.41 eV. Initially, individual sub-cell improvement was carried out through varying the solar cell's parameters, starting with the absorber thickness, the ETL and HTL electron affinities, and the capture cross-section. Then, The tandem solar cell is then constructed using these individually optimized sub-cells. A current matching JSC of 16.71 mA/cm2 was produced between the top and bottom sub-cell thickness of 220 nm and 1400 nm, respectively. The tandem device simulation with CsGeI3 on FASnI3 yielding a PCE of 30.42%, Voc= 2.12 V; Jsc= 16.71 mA/cm2, and FF= 85.87%, that was much greater than each sub-cells output. The findings of this study demonstrate the possibility of using lead-free perovskite, such as FASnI3, to produce high PCE in tandem devices. © 2024 Elsevier GmbH