Degradation Evolution of Perovskite Solar Cells via In Situ Real‐Time Optical Observation.

Understanding the degradation kinetics of perovskite materials in operating perovskite solar cells (PSCs) is critical for developing methods to further enhance their device stability. However, it remains a challenge to capture the details and characteristics of the perovskite degradation process inside operating PSCs under different environmental conditions in real‐time at the microscopic scale. Herein, a novel, nondestructive real‐time in situ monitoring method based on a tapered seven‐core fiber optic sensor is demonstrated. The fiber‐optic sensor can be facilely inserted near the surface of the perovskite layer of a working PSCs to monitor its degradation kinetics without interfering with the performance of the device. Stable and reproducible correlations between real‐time material degradation and optical wavelength response under different humidity and temperature conditions are observed and quantified. This new measurement tool allows real‐time access to the detailed degradation evolution of PSCs, which not only guides the design of more stable devices but also offers the possibility to monitor the health status of PSCs in field applications. [ABSTRACT FROM AUTHOR]