Impact of Hexagonal Boron Nitride Encapsulation on the Photophysical Dynamics of MAPbI₃ Perovskite Crystals

Metal halide perovskites are known to suffer from instability due to their high sensitivity to external stimuli. Although encapsulation can considerably improve their stability, the impact of encapsulation on the intrinsic photophysical properties of perovskites remains unclear. Here, we investigate the effect of hexagonal boron nitride (hBN) encapsulation on the photoluminescence (PL) dynamics of MAPbI₃ perovskite crystals at the individual crystal level. The results demonstrate that hBN encapsulation leads to PL decline, PL lifetime shortening, and spectral broadening in MAPbI₃ crystals, which can be ascribed to the stress exerted by hBN encapsulation on MAPbI₃ crystals that promotes defect formation and subsequent nonradiative recombination losses. Furthermore, although hBN encapsulation can delay degradation, the effect of hBN-induced stress and the poor sealing due to single-sided encapsulation would further broaden the spectra over time. This work provides new insights into the photophysical effects of encapsulation on perovskites and has significance for the selection of perovskite encapsulation strategies.