Applying time-resolved photoluminescence in scanning near-field optical microscopy to map charge-carrier dynamics in CsPbBr3 nanocrystals

Charge-carrier dynamics in perovskite materials are commonly investigated using techniques that either provide spatially averaged information or probe only a single point, often overlooking nanoscale heterogeneities that critically influence device performance. In this work, time-resolved photoluminescence mapping in aperture-type scanning near-field optical microscopy was used to directly visualize charge-carrier behavior in CsPbBr3 nanocrystal films, achieving sub-diffraction spatial resolution of ∼150 nm and temporal resolution of 100 ps. Through the combination of near-field optical excitation and simultaneous topographical characterization, structural features were found to influence local optical and electronic properties. Spatial variations in photoluminescence intensity, emission wavelength, and carrier lifetimes were observed across quasi-continuous films formed by nanocrystal aggregation. These heterogeneities, which are highly relevant to optoelectronic and photonic applications, were shown to significantly affect carrier recombination dynamics. Notably, regions exhibiting redshifted emission were found to have longer photoluminescence lifetimes, indicating a strong correlation between spectral properties and recombination processes. This study demonstrates how near-field time-resolved photoluminescence can serve as a powerful tool to probe local charge-carrier dynamics in perovskite materials and offers new insights for their more reliable and efficient integration into next-generation optoelectronic technologies.