Nanochemical Investigation of Degradation in Organic–Inorganic Hybrid Perovskite Films Using Infrared Nanoscopy

The degradation of organic–inorganic hybrid perovskite (OHP) films is a crucial issue in OHP optoelectronics. Herein, we investigate the degradation process of OHP films by simultaneous measurement of topography and infrared absorption mapping images using photothermal induced resonance spectroscopy. By tracking the intensity of molecular vibration, we found that oxygen and moisture are easily attached at the grain boundary (GB) rather than at the grain interior of the OHP film. These data are well matched with photoluminescence (PL) mapping images, which show that the PL intensity of PbI2 as an indicator of degradation is relatively intense at the GB. Thus, by using correlated structural, chemical, and optical analyses, we confirm that the degradation of the OHP film is initiated at the GB through the attached oxygen molecules and moisture. We expect that this study will contribute to solving the degradation issue and enhancing the stability of OHP optoelectronics.