Surface Characterization of the Solution‐Processed Organic–Inorganic Hybrid Perovskite Thin Films

• Published in: Small (Weinheim an der Bergstrasse, Germany) Vol. 18; no. 47; pp. e2204271 - n/a
• Main Authors: Zhao, Han, Ma, Kang, Li, Jianmin, Fu, Yikai, Qin, Ying, Zhao, Dongbing, Dai, Haitao, Hu, Zhixin, Sun, Zhixiang, Gao, Hong‐Ying
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 01.11.2022
• Subjects: Configuration management; Crystal defects; Density functional theory; Flat surfaces; Grain boundaries; Iodine; ion migration; Nanotechnology; Optoelectronics; organic–inorganic hybrid perovskites; Passivity; Perovskites; Scanning tunneling microscopy; solution‐processed; Surface properties; surface structures; Thin films
• ISSN: 1613-6810; 1613-6829; 1613-6829
• DOI: 10.1002/smll.202204271

The surface properties of organic–inorganic hybrid perovskites can strongly affect the efficiency and stability of corresponding devices. Even though different surface passivation methods are developed, the microscopic structures of solution‐processed perovskite film surfaces are not systematically studied. This study uses low‐temperature scanning tunneling microscopy to study the organic–inorganic hybrid perovskite thin films, MA0.4FA0.6PbI3 and MAPbI3, synthesized by the spin‐coating method. Flat surface structures, atomic steps, and crystal grain boundaries are resolved at an atomic resolution. The surface imperfections are also characterized, as well as the dominant defects. Simulations on different types of iodine vacancy configurations are performed by density functional theory calculations. In addition, it is observed that the surface iodine lattice structure is unstable during scanning. Tip scanning can also cause the vertical migration of surface iodine ions. The measurements provide the direct visualizations of the surface imperfections of the solution‐processed perovskite films. They are essential for understanding the surface‐related optoelectronic effects and rationally designing more efficient surface passivation methods. The atomically resolved microscopic surface structures of solution‐processed metal halide perovskite thin films are characterized by the low‐temperature scanning tunneling microscopy. Different types of surface vacancy defects are observed and simulated by density functional theory calculations, and it is shown that the internal defects can be healed by tip induced ion migrations.