Spectral Contributions to Circularly Polarized Luminescence beyond Artifacts in Solution-Processed Thin Films

Circularly polarized luminescence (CPL) spectroscopy is a powerful tool used for probing the preferential emission of left and right circularly polarized light from chiral luminescent materials. Accurate interpretation of CPL spectra remains challenging, however, owing to relatively small signal intensity and artifact-laden responses along with linear anisotropy and birefringence effects associated with sample anisotropy. Herein, we demonstrate that additional spectral features become manifest in the CPL spectra of chiral perovskite thin films, an emerging material with potential in sensing, catalysis, data storage, and advanced display applications. CPL spectra show discrete transitions with varying sign and are attributed to the coexistence of crystalline perovskite, intermediate, and precursor phase domains formed during non-uniform crystallization, each contributing independently to the ensemble-averaged signal. These findings are corroborated by microspectrophotometry measurements, which directly resolve these spatially distinct domains and their characteristic absorbance profiles. Collectively, this work underscores the importance of accounting for coexisting emissive components when interpreting CPL spectra of solution-processed thin films.