An investigation of hole transport layers and electron transport layers to produce highly efficient K₂TiI₆-based perovskite solar cells

In this theoretical study, potential K₂TiI₆ perovskite material has been used as the absorber layer of the investigated perovskite solar cells (PSCs). The SCAPS-1D program was used to conduct the numerical analysis where 10 different hole transport layers (HTLs) and 4 electron transport layers (ETLs) were used to find the best optimum device structure. While various HTLs were studied, D-PBTTT-14 showed the best-optimized performance and therefore it was chosen as the final HTL material for further studies in combination with 4 ETL materials. Different device parameters such as the thickness of the absorber, HTL, and ETL layers; doping concentrations, and defect densities are varied in this work to optimize the investigated device structures. Moreover, the effect of temperature, series and shunt resistance, J-V curve, Q-E curve, recombination and generation rates were explored in this study. After optimizing various device parameters, the device with CdZnS ETL demonstrated superior performance compared to other ETL devices. It achieved a power conversion efficiency (PCE) of 26.21%, fill factor (FF) of 88.06%, short-circuit current density (J_sc) of 20.951 mA/cm², and an open-circuit voltage (V_OC) of 1.4205 V. Under fully optimized conditions, LBSO, Nb₂O₅, and PC₆₀BM ETL devices showed PCE of 22.06%, 23.24%, and 23.12%, respectively. Based on the findings of this study, it can be stated that this work could be valuable for the practical implementation of K₂TiI₆ absorber-based PSCs.