Constructing Layered 1D/3D Heterostructure for Efficient and Stable Single‐Crystal Perovskite Photovoltaics

ABSTRACT Low‐dimensional/three‐dimensional (LD/3D) heterostructures represent an effective strategy for suppressing surface defects and ion migration in metal halide perovskite solar cells (PSCs), however, one‐ and two‐dimensional (1D and 2D) perovskite layers suffer from incomplete coverage and low ion migration barrier, respectively. Herein, a 1D perovskite crystal with layered structure is designed by employing 4‐(3‐phenylpropyl)pyridine (4PPY) with ordered large‐cation arrangement and octahedral isolation. The as‐prepared (4PPY)PbI 3 crystals preserve a high ion migration activation energy ( E a ) of 1D perovskites and exhibit excellent surface coverage as 2D perovskites. Moreover, superior water stability is observed, which helps prevent permeation of iodide ions across the LD perovskite layer. When applying (4PPY)PbI 3 as a blocking layer on Cs 0.05 FA 0.95 PbI 3 (FA = CH(NH 2 ) 2 ) single crystals, interface iodide ion migration is suppressed more effectively than using both 1D and 2D perovskites. As a result, the encapsulated single‐crystal PSC devices can remain 100% of the initial efficiency after 1032 h of continuous light illumination. Besides, power conversion efficiency (PCE) is increased from 23.8% to 25.4%, due to the mitigation of surface iodide ion vacancies and nonradiative recombination. These results highlight the potential of layered 1D perovskites for constructing LD/3D heterostructures, which is instructive for developing efficient and durable PSCs.