Photoluminescence Degradation in Metal Halide Perovskites: Is In‐Situ Study with Concentrated Sunlight Possible?

Photoluminescence (PL) spectroscopy is a valuable tool fordegradation studies of perovskite‐based photovoltaic materials. The wavelength‐sensitive nature of the photo‐induced processes implies a preference for sunlight as the photo‐excitation source for such PL studies. This study reports on the design and experimental validation of a new setup for the in situ study of PL degradation in metal halide perovskites using concentrated natural sunlight in a wide range of solar concentrations and sample temperatures. The system allows the sample to be excited with the entire solar spectrum while successfully filtering undesired reflected sunlight using two orthogonal polarization filters. Depending on temperature and solar concentration, we observed three types of perovskite PL behavior: stable PL response, without degradation; reversible PL degradation with stable ultraviolet–visible light absorption; and nonreversible PL degradation accompanied with the variation of light absorption.