Numerical Simulation and Optimization of Lead-Free CsGeI2Br/FASnI3 Dual-Absorber Perovskite Solar Cell with Organic Charge Transport Layer

Abstract

As demand grows for high-efficiency, affordable, and eco-friendly photovoltaic technology, alternative materials such as CsGeI2Br and FASnI3 can play a significant role. Tin (Sn) and germanium (Ge) based materials can be promising substitutes for lead (Pb) based materials in the development of Perovskite solar cells (PSC) due to their superior optical properties, higher carrier mobility, and better performance. This research aims to enhance the efficiency of CsGeI2Br/FASnI3 double absorber-based (PSC), where PCBM was used as the ETL and PTAA as the HTL. The analysis was conducted by varying the absorber layer's thickness, doping density, and defect density using the SCAPS-1D numerical simulator and investigating the influence on key performance parameters such as power conversion efficiency (PCE), short circuit current density (Jsc), open circuit voltage (Voc) and fill factor (FF). Before optimization the device structure (FTO/PCBM/CsGeI2Br/FASnI3/PTAA/Au) provide a PCE of 21.20%, Jsc of 28.70 (mA/cm2), Voc of 1.16 V and FF of 63.63% but after considering the standard optimized parameters the device achieved a PCE of 35.00%, Jsc of 30.44 (mA/cm2), Voc of 1.30 V and FF of 88.46%. Additionally, to evaluate the optimized device's reliability and stability, the following analyses are performed: temperature (T), series resistance (Rs), and shunt resistance (Rsh). The simulation outcomes were validated through comparison with prior research. The proposed device structure not only achieved superior performance but is also lead-free and cost-effective. The results demonstrate the potential of lead-free Sn /Ge-based perovskite architectures for high-performance and environmentally preferable photovoltaic applications.