In Situ Vapor‐Phase Halide Exchange of Patterned Perovskite Thin Films

• Published in: Small (Weinheim an der Bergstrasse, Germany) Vol. 17; no. 11; pp. e2006737 - n/a
• Main Authors: Kim, Geemin, An, Sol, Hyeong, Seok‐Ki, Lee, Seoung‐Ki, Kim, Myungwoong, Shin, Naechul
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 01.03.2021
• Subjects: anion exchange; Chemical vapor deposition; Composition; diffusion; Exchanging; metal halide perovskites; Metal halides; Nanotechnology; Optoelectronic devices; patterning; Perovskites; Phase transitions; photodetectors; Structural stability; Substrates; Thin films; photodetectors; diffusion; anion exchange; patterning; chemical vapor deposition; metal halide perovskites
• ISSN: 1613-6810; 1613-6829
• DOI: 10.1002/smll.202006737

Metal halide perovskites (MHPs) exhibit optoelectronic properties that are dependent on their ionic composition, and the feasible exploitation of these properties for device applications requires the ability to control the ionic composition integrated with the patterning process. Herein, the halide exchange process of MHP thin films directly combined with the patterning process via a vapor transport method is demonstrated. Specifically, the patterned arrays of CH3NH3PbBr3 (MAPbBr3) are obtained by stepwise conversion from polymer‐templated PbI2 thin films to CH3NH3PbI3 (MAPbI3), followed by halide exchange via precursor switching from CH3NH3I to CH3NH3Br. It is confirmed that the phase transformation from MAPbI3 patterns to MAPbBr3 shows time‐ and position‐dependences on the substrate during halide exchange following the solid‐solution model with Avrami kinetics. The photodetectors fabricated from the completely exchanged MAPbBr3 patterns display exceptional air stability and reversible detectivity from “apparent death” upon removing the adsorbed impurities, thereby suggesting the superior structural stability of perovskite patterns prepared through vapor‐phase halide exchange. The results demonstrate the potential of chemical vapor deposition patterning of MHP materials in multicomponent optoelectronic device systems. An in situ vapor‐based halide exchange of the metal halide perovskite thin film patterns is demonstrated via stepwise conversion from PbI2 patterns to CH3NH3PbI3, directly followed by halide exchange via precursor switching (CH3NH3I → CH3NH3Br). Photodetector devices prepared from the completely exchanged CH3NH3PbBr3 exhibit remarkable stability to air exposure and reversible performance via Br passivation of grain boundaries.