Analysing thickness and doping dependent photovoltaic performance in double perovskite (cesium tin iodide) solar cells: A TCAD-based simulation study

In this study, the effects of the electron transport layer (ETL) material, thickness and acceptor doping of the active layer on the performance of HTL-free Cs 2 SnI 6 double perovskite solar cells (PSCs) are investigated through numerical simulations. These simulations were performed using Silvaco-TCAD. Among the ETLs studied, ZnSe ETL offers a superior power conversion efficiency (PCE) of 19.06% compared with 17.8% of TiO 2 . An increase in the active layer thickness markedly elevates the short circuit current density (J SC ), which saturates at 30.8 mA/cm 2 for a thickness of 700 nm. The device also preserves a high fill factor (FF) of 84.3% and an open-circuit voltage (V OC ) of 0.92 V. We also show that further improvement in the PSCs performance is possible by optimizing the acceptor concentration of the active layer. Both V OC and FF improve significantly with increasing doping concentration. The optimum PCE of 27.3% is obtained at an acceptor density of 10 20 cm −3 . The variations in photovoltaic parameters with thickness and doping concentration are explained on the basis of fundamental device physics and analytical expressions. More importantly, we show that active layer doping controls the internal electric field, junction behaviour, and charge recombination. Therefore, tuning the acceptor doping level of the active layer can be an effective approach for improving the performance of HTL-free PSCs.