Enhancing the performance and stability of carbon-based CsPbI2Br perovskite solar cells via tetrabutylammonium iodide surface passivation

Abstract All-inorganic carbon-based perovskite solar cells (C-PSCs) with CsPbI2Br as photosensitizer have attracted great attention due to their low cost, high efficiency, and good stability. However, the CsPbI2Br film prepared by the solution method usually has many defects, which reduces the charge extraction rate and photoelectric performance. In this paper, intermediate gradient annealing and antisolvent ethyl acetate treatment are combined to prepare CsPbI2Br films with good crystallinity and few voids. The surface of the obtained CsPbI2Br film is then treated using tetrabutylammonium iodide (TBAI), which can interact with the Pb-I framework to passivate defect states and extend the carrier lifetime. Finally, the champion power conversion efficiency (PCE) of the optimized C-PSCs with a structure of FTO/SnO2/CsPbI2Br/carbon electrode prepared in the air reach 12.29%. At the same time, TBAI molecules also effectively enhance the stability of the PSCs, and the unencapsulated device can still maintain 90% of the initial efficiency after 300 h of storage in an ambient air atmosphere with a relative humidity of 20%-30%. This work provides a simple and effective strategy for the preparation of cheap, high-performance, and stable all-inorganic C-PSCs under atmospheric conditions, and also increases the feasibility of PSCs commercialization.