The Hole Transport Layer Material Optimization for an Efficient Lead-Free Double Perovskite Cs2AgBiBr6 Based Solar Cell by Numerical Simulation

Lead-free double perovskites have recently emerged as a promising alternative material for solar cell applications, exhibiting encouraging optoelectronic properties, high environmental stability, and low toxicity. In this manuscript, we report the effect of different hole transport layer materials on the photovoltaic performance of lead-free double perovskite solar cells. Optimization of hole transport layers (HTLs) is performed by correlating the open-circuit voltage (Voc) with the built-in potential (Vbi). It is revealed from the simulation results that higher Vbi resulted in higher Voc. Also, it is found that for proper selection of HTLs, EV_HTL (valence band maximum of HTL) and φBC (work function of back contact) should not be much deeper than EV_PVK (valence band maximum of a double perovskite layer) to avoid Vbi loss. In the present study, FTO/TiO2/Cs2AgBiBr6/HTLs/Cu device was designed, and Solar Cell Capacitance Simulator (SCAPS-1D) was used for one-dimensional simulation and analysis. An active layer of 0.3 µm was used for the present work. Photovoltaic power conversion efficiency (PCE), Voc, Jsc, and FF were obtained using numerical simulation. The most suitable hole transport layer material was found to be Spiro-OMeTAD. Moreover, under optimized conditions, the device PCE increased to 3.75 %. The optimized photovoltaic performance of the device is as follows: open-circuit voltage Voc = 7.2412 V, short-circuit current density Jsc = 8.02965 mA/cm2, and fill factor FF = 6.45 %. Overall, the encouraging simulation results achieved in this study will provide insightful guidance for replacing the commonly used carcinogenic Pb-based perovskite with eco-friendly, highly efficient inorganic perovskite solar cells.