The joint effect of spin–orbit coupling and atomistic disorder on bandgap evolution in inorganic CsSn1−xPbxI3 mixed perovskite

Although the highest power conversion efficiency of an all-inorganic perovskite solar cell has surpassed 20%, the efficiency gap compared with the hybrid perovskite device is still noticeable. The main electronic deficiency of all-inorganic perovskite for improving high efficiency is its larger energy band value. By studying the change of bandgap of inorganic perovskite with the composition ratio, it can help us to optimize the photoelectron performance of perovskite solar devices. Based on first-principles calculations, it is found that the degree of band curvature of the mixed CsSn1−xPbxI3 bandgap is small due to the joint effect of spin–orbit coupling and atomistic disorder, which is different from the bandgap evolution of a hybrid perovskite system. The bandgap bowing parameter gradually augments with an increasing MA+ ratio. Our results indicate that component engineering and electronic structure modulation can optimize the photovoltaic performance appropriately.