Designing and optimizing the lead-free double perovskite Cs2AgBiI6/Cs2AgBiBr6 bilayer perovskite solar cell

Due to their potential to be an absorber layer in perovskite solar cells with cheap cost, outstanding stability, and high efficiency, lead-free double perovskite Cs₂AgBiI₆ and Cs₂AgBiBr₆ have attracted tremendous attention recently. In this work, Cs₂AgBiI₆ and Cs₂AgBiBr₆ are introduced to create a perovskite-perovskite bilayer solar cell FTO/ETL/Cs₂AgBiI₆/Cs₂AgBiBr₆/HTL/Au through SCAPS-1D. The Cs₂AgBiI₆/Cs₂AgBiBr₆ double absorber layer structure significantly reduces lead toxicity while improving the device’s stability and light absorption capabilities, according to the results. We chose the optimal hole transport layer (HTL) and electron transport layer (ETL) to examine the impacts of several HTLs and ETLs on the PSC. The device’s performance appears to be significantly impacted by the energy level alignment of the absorber and transport layers, and that ideal energy band structure facilitates the carriers’ transportation and separation. Through numerical simulations, the impacts of some factors containing the absorber layer thickness, defect density and doping concentration of the perovskite layers, operating temperature, and different back-contact electrodes, were examined. The optimized results are PCE = 34.36 %, FF = 93.35 %, J_sc = 24.78 mA/cm², and V_oc = 1.48 V. This work demonstrates that double perovskite Cs₂AgBiI₆ and Cs₂AgBiBr₆ hold great potential for application in photovoltaic and optoelectronic devices.