Enhancing Stability and Efficiency of CsPbI3 Perovskite Solar Cells via 3-(Aminomethyl)piperidinium Pretreatment

The inorganic perovskite cesium lead triiodide (CsPbI3) has a bandgap of 1.73 eV, making it suitable for the top cell in perovskite tandem solar cells. Additionally, the single halide composition of inorganic perovskite offers advantages in halide segregation and thermal stability compared to light-harvesting layers with mixed halides. However, achieving high performance in CsPbI3 perovskite solar cells (PSCs) remains challenging, as their efficiency is still lower than that of halide-mixed PSCs. This is primarily due to severe energy losses caused by various defects, such as vacancies and anti-site defects, occurring on the surface and grain boundaries. A common approach to managing these defects in the light absorber layer is to utilize 2D perovskites, but the high crystallization temperature of CsPbI3 prevents introduction of organic spacer. Here, we propose a pretreatment with 3-(aminomethyl)piperidinium (3AMP) before depositing the CsPbI3 film. The 3AMP molecule is predicted to be effective in controlling defects in CsPbI3-based PSCs, because of thermal stability compared to common 2D perovskite organic spacers such as butylammonium. By introducing thermally stable 3AMP, we observed changes in the crystallographic and interfacial properties, resulting in an improved power conversion efficiency of over 21% and an open-circuit voltage of 1.21 V. Additionally, devices treated with 3AMP showed improved stability compared to control devices.