Manipulating the Formation of 2D/3D Heterostructure in Stable High-Performance Printable CsPbI 3 Perovskite Solar Cells.

Manipulating the formation process of the 2D/3D perovskite heterostructure, including its nucleation/growth dynamics and phase transition pathway, plays a critical role in controlling the charge transport between 2D and 3D crystals, and consequently, the scalable fabrication of efficient and stable perovskite solar cells. Herein, we demonstrated the fabrication of a 2D/3D layered structure for stable and high-performance ambient-printed CsPbI 3 solar cells based on a series of organic ligands. Using time-resolved X-ray diffraction, the structural evolution and phase transition pathways of the ligand-dependent 2D perovskite atop the 3D surface were revealed. The results show that the ligand size and shape have a critical influence on the final 2D structure. In particular, ligands with smaller sizes and more reactive sites tend to form the n = 1 phase. Increasing the ligand size and decreasing the reactive sites promoted the transformation from 3D to n = 3 and n<3 phases. These findings are useful for the rational design of the phase distribution in 2D perovskites to balance the charge transport and stability of the perovskite films. Finally, solar cells based on ambient-printed CsPbI 3 with n-butylammonium iodide treatment achieved an improved efficiency of 20.33%, which is the highest reported value for printed inorganic perovskite solar cells. This article is protected by copyright. All rights reserved.