Role of Organic HTLs in Pushing Ag₃BiI₆ Solar Cells to New Heights by Combining Experiment and Simulation: Achieving Maximum Efficiency

In recent years, Ag3BiI6 materials have gained popularity because of their low cost, high element abundance, and environmental friendliness. For the first time, this study was to determine the best organic hole-transport layer (HTL) for FTO/(c+mp)TiO2/Ag3BiI6/HTLs/Au structure, among well-known options like Spiro-OMeTAD, PTAA, P3HT and PEDOT:PSS by integrating experimental and simulation techniques. A single-step spin-coating process was used on FTO substrates to deposit the first (c+mp) TiO2 layer, followed by the Ag3BiI6 layer. After depositing, the films were analyzed for structural properties, thickness, optical properties, and surface morphology by X-ray diffraction (XRD), Dektak, ultraviolet–visible (UV–vis), and scanning electron microscopy (SEM). Additionally, solar cell capacitance simulator in one dimension (SCAPS-1D) simulations have been used to study the effects of aligning band energies, current density voltage (J–V) characteristics, quantum efficiency (QE), capacitance frequency (C–f), as well as generation and recombination rates. This study revealed that the device architectures of the investigated device types were greatly influenced by several factors, such as the Ag3BiI6 thickness and total defect density, as well as the specific HTL employed in the device design. It was found that by meticulously optimizing the total defect density and thickness of the absorbing layer and HTLs, notable improvements in efficiency were achieved for Spiro-OMeTAD (8.49%), PTAA (7.27%), P3HT (7.62%), and PEDOT:PSS (6.97%). The optimized performance has nearly doubled the performance of the initial structure, leading to a significant improvement in the FTO/(c+mp)TiO2/Ag3BiI6/HTLs/Au configuration. The numerical simulations of Ag3BiI6 solar cells, in combination with experimental investigations have not yet been reported.