Design and Simulation of Cs₂BiAgI₆ Double Perovskite Solar Cells with Different Electron Transport Layers for Efficiency Enhancement

Lead-free Cs2BiAgI6 has garnered a lot of research interest recently due to its suitability as a potential absorber layer in the solar cell (SC) architecture owing to its low cost, good stability, and high efficiency. The main highlight of this research work includes the photovoltaic (PV) performance enhancement of Cs2BiAgI6 double perovskite solar cells (PSCs) by optimizing the optoelectronic parameters of the absorber, electron transport layer (ETL), hole transport layer (HTL), and various interface layers. Solar Cell Capacitance Simulator One dimension (SCAPS-1D) numerical simulation was used to optimize the performance of Cs2BiAgI6 absorber-based SCs consisting of copper barium thiostannate (CBTS) as the HTL and TiO2, PCBM, ZnO, IGZO, SnO2, and WS2 as ETLs. The role of the non-lead cesium-based halide perovskite absorber layer in the improvement of the SC performance was systematically investigated through a variation in the thickness, doping density, and defect density of the absorber layer, ETL, and HTL. The performance of the investigated device architectures is largely dependent on the thickness of the absorber layer, acceptor density, defect density, and the combination of different ETLs and HTLs. We found that TiO2, PCBM, ZnO, IGZO, SnO2, and WS2 ETL-based optimized devices recorded a power conversion efficiency (PCE) of 23.14, 23.71, 23.69, 22.97, 23.61, and 21.72%, respectively. Furthermore, the effect of series and shunt resistances, temperature, capacitance, and Mott–Schottky for the six optimized devices was estimated along with the computation of the corresponding generation and recombination rates, current density–voltage (J–V), and quantum efficiency (QE) characteristics. The PV parameters obtained from this comprehensive analysis are finally compared with the earlier published theoretical and experimental reports on Cs2BiAgI6 absorber-based SCs.