A Combined Experimental and Simulation Study on Defect Passivation and Crystallization Assisted by a Novel Organic Dye for Efficient Perovskite Solar Cells

In recent years, there has been an increasing focus on all-inorganic perovskite solar cells (PSCs) as a potential solution to the thermal instability of organic–inorganic PSCs. In contrast, the photovoltaic performance of PSCs is limited by the existence of a significant number of ionic defects on the surface and grain boundaries, which function as nonradiative recombination centers, resulting from a solution deposition procedure that provides a polycrystalline characteristic to perovskite films. In this study, highly effective and stable inorganic PSCs based on CsSnI2Br compositional perovskite are fabricated using Rose Bengal (RB), an organic dye, as a passivator. The phenolic hydroxyl group and carboxylic acid groups of RB serve to reduce trap states by interacting with undercoordinated negative and positive ions. Additionally, they have a notable impact on enhancing the grain size and crystallinity of perovskite films. As a result, we obtained perovskite films with excellent optoelectronic properties, a longer carrier lifetime, a lower trap density, and enhanced stability. Consequently, the open-circuit voltage (VOC) rose from 0.87 to 0.94 V, and the power conversion efficiency (PCE) increased from 7.40% to 9.41%, representing a moderate yet meaningful enhancement under ambient, unencapsulated conditions. In addition, numerical SCAPS-1D simulations are conducted to compare the experimental photovoltaic performance. Although the devices manufactured according to the ideal specifications do not correspond to the observed experimental trends, by feeding the experimental values into SCAPS-1D, we can analyze the major challenges in the current–voltage characteristics of the device.