Deciphering Phase Growth Direction of Perovskite Thin Films for Opto-Electronic Applications

Obtaining high-performance metal-organohalide (MHP) perovskite films of various dimensions suitable for different applications remains a challenge. Due to the instability of 3D MHP, there is a growing interest in lower-dimensional MHPs such as Quasi-3D, Quasi-2D, and 2D structures. Despite the extensive experimental research and knowledge gathered on preparing these films for optoelectronic applications, the growth direction of different phases during film formation remains not fully understood. Then, we have comprehensively analyzed the internal phase changes of 2D to 3D perovskites during thermal annealing by mainly using insitu GIWAXS. Our original findings reveal various 2D phases grow downward while 3D/quasi-3D (high n) phases grow laterally. Additionally, the number and quantity of 2D phases vary with the annealing time. By revealing the phases growth mechanism, a clear map of optimization to produce high-performance perovskite films in the future is revealed.