Achieving efficiency above 30% with new inorganic cubic perovskites X2SnBr6 (X = Cs, Rb, K, Na) via DFT and SCAPS-1D

Abstract

The solar sector is increasingly focusing on inorganic cubic halide perovskite materials without lead (Pb) because of their exceptional structural, electronic, and optoelectronic properties. At the first phase, we thoroughly examined the structural, electronic, and optical characteristics of X2SnBr6 (X = Cs, Rb, K, Na) in detail using FP-DFT in this manuscript. Additionally, we assessed their photovoltaic performance utilizing the SCAPS-1D simulator software. Based on our observations, it has been noted that each of the materials exhibits a direct band gap at the G (Gamma)-point, favorable tolerance factors, negligible losses, and outstanding absorption coefficients. Hence, their potential applications extend to photovoltaic cells and diverse optoelectronic devices. Consequently, we employed the SCAPS-1D simulator to conduct a thorough evaluation of the photovoltaic performance in solar cell configurations based on Cs2SnBr6, Rb2SnBr6, K2SnBr6, and Na2SnBr6 absorbers, incorporating a TiO2 ETL layer. This examination included altering the thickness, defect densities, and levels of doping. The top power conversion efficiencies (PCE) achieved were 29.22% for Cs2SnBr6, 27.25% for Rb2SnBr6, 30.62% for K2SnBr6, and 29.51% for Na2SnBr6 absorber layers, accompanied by VOC values of 1.0246, 0.8713, 0.8345, and 0.7741V; JSC values of 32.2656, 36.7150, 42.6921, and 45.484 mA/cm2; and FF values of 88.38, 85.18, 85.96, and 81.85%, respectively. Our findings indicate that changes in the size of the X-cation significantly impact the bandgap energy, band structure, and optoelectronic properties with the performance of solar cells. Therefore, this study contributes to the progress of lead-free hybrid solar cells and various other categories of optoelectronic devices.