Strain‐Induced, Thermally Tunable Light‐Heavy Hole Emission of Perovskite Nanocrystal‐Based Heterostructure

Abstract Understanding the role of strain in the electronic structure and emission of encapsulated perovskite nanocrystals (PNCs) is critical for their light‐emitting application. Herein, photoluminescence (PL) and the structure of Type‐I CsPbBr 3 @PbBrOH are explored by a combination of temperature‐dependent optical spectroscopy with x‐ray diffraction analysis. The results reveal that the anisotropic lattice mismatch of embedded CsPbBr 3 NC with the PbBrOH matrix induces an asymmetric strain. The asymmetric strain increases significantly at low temperatures due to the different thermal response of CsPbBr 3 and PbBrOH, where the former undergoes a structural transition between two different orthorhombic phases, while the latter is only subjected to a continuous thermal shrinkage. The asymmetric strain lifts the light hole‐heavy hole (LH‐HH) degeneracy of CsPbBr 3 , which introduces novel radiative recombination pathways and gives rise to PL spectral splitting. This study unveils the asymmetric strain‐triggered PL spectral splitting and thermal tuning of the emission in PNC‐based heterostructure, which not only provides an in‐depth understanding of the fundamental properties of perovskite but also opens a gate for developing perovskite‐based multi‐color light sources.