A Key 2D Intermediate Phase for Stable High-Efficiency CsPbI2Br Perovskite Solar Cells

Inorganic CsPbI2Br perovskite is promising for solar cell applications due to its excellent thermal stability and optoelectronic characteristics. Unfortunately, the current high-efficiency CsPbI2Br perovskite solar cells (PSCs) are mostly fabricated in an inert atmosphere due to their instability to moisture. Herein, a low-dimensional intermediate-assisted growth (LDIAG) method is reported for the deposition of CsPbI2Br film in ambient atmosphere by introducing imidazole halide (IMX: IMI and IMBr) into the precursor solution to control both nucleation and growth kinetics. The IMX first combines with PbI2 in the precursor film to form a 2D intermediate which then gradually releases PbI2 to slowly form high-quality CsPbI2Br film during annealing. It is found that the LDIAG method produces a uniform, highly crystalline, pinhole-free, and stable CsPbI2Br film with low defect density. Consequently, the solar cell efficiency is increased to as high as 17.26%, one of the highest for this type of device. Furthermore, the bare device without any encapsulation shows excellent long-term stability with approximate to 86% of its initial efficiency retained after being exposed to the ambient environment for 1000 h. This work provides a perspective to tune the intermediate phases and crystallization pathway for high-performance inorganic PSCs formed under ambient conditions.

Automated summary

In this study, a low-dimensional intermediate-assisted growth (LDIAG) method was developed to deposit high-quality and stable CsPbI2Br film in ambient atmosphere by introducing imidazole halide (IMX) to control nucleation and growth kinetics. The solar cell efficiency was improved to 17.26% using this method, showcasing potential for high-performance inorganic perovskite solar cells formed under ambient conditions.