Vertically Arranged Internal Grains and Superior Surface Textures of Perovskite Films Enabled by Ligand–Solvent Engineering.

Ligand‐solvent engineering has been widely applied to improve the quality of perovskite films by forming intermediate films. However, there is an inconsistent understanding in the studies on the composition and mechanism of intermediate films formed by different ligand solvents, and the influence on perovskite film morphology is still elusive. Herein, the pure intermediate films (composed of pure crystal nucleus and amorphous precursor) are fabricated by the addition of ligand solvents with different coordination abilities. Notably, a single heterogeneous nucleation process is induced by the pure intermediate film, resulting in the formation of vertically arranged internal perovskite crystals with few horizontal boundaries, that improve charge transfer and device performance. Furthermore, the small and uniform crystals obtained by adding a ligand solvent with weak coordination ability result in smooth films and a smaller device current (Jsc = 22.74 mA cm−2, PCE = 19.58%). In contrast, the large and uneven crystals obtained by strong coordination ability lead to rough films and a larger device current (Jsc = 23.24 mA cm−2, PCE = 20.72%). This study is devoted to providing a significance reference for the fabrication of perovskite films with vertically arranged internal grains and superior surface textures. [ABSTRACT FROM AUTHOR]