Efficient Energy Transfer Between Ligand‐Free FAPbBr ₃ Nanocrystals in a Mesoporous SiO ₂ Matrix

Abstract Lead halide perovskite nanocrystals (NCs) are promising materials for next‐generation optoelectronic devices due to their exceptional optical properties. However, poor long‐term stability remains a major challenge. In this study, formamidium lead bromide (FAPbBr 3 ) NCs are embedded in a mesoporous silica matrix to enhance stability and explore exciton transport mechanisms. These NCs display a narrow photoluminescence (PL) linewidth of 25 meV at 7 K. The absence of surface ligands leads to reduced interparticle spacing, favoring non‐radiative Förster resonance energy transfer (FRET) as the dominant exciton transport mechanism. Using time‐resolved and spectrally‐resolved PL spectroscopy at cryogenic temperatures, it is observed significant spectral redistribution over time, indicating energy transfer from higher‐energy to lower‐energy NCs. To quantitatively interpret these dynamics, a theoretical model based on a 2D array of coupled NCs, incorporating Förster's theory to simulate exciton diffusion is employed. This model successfully reproduces the experimentally observed PL decay behavior, confirming FRET‐mediated exciton transport with an upper‐limit efficiency close to 100% and a transfer rate of 105 ns −1 . These findings offer key insights into energy transfer processes in ligand‐free perovskite NC systems and underscore the potential of mesoporous silica matrices for improving stability and enabling control over excitonic interactions in perovskite‐based optoelectronic applications.