Pressure-induced Emission in 0D Metal Halide (EATMP)SbBr5 by Regulating Exciton–Phonon Coupling

Zero-dimensional (0D) hybrid metal halides are considered as promising light-emitting materials due to their unique broadband emission from self-trapped excitons (STEs). Despite substantial progress in the development of these materials, the photoluminescence quantum yields (PLQY) of hybrid Sb-Br analogs have not fully realized the capabilities of these materials, necessitating a better fundamental understanding of the structure–property relationship. Here, we have achieved a pressure-induced emission in 0D (EATMP)SbBr5 (EATMP = (2-aminoethyl)trimethylphosphanium) and the underlying mechanisms are investigated using in situ experimental characterization and first-principles calculations. The pressure-induced reduction in the overlap between STE states and the ground state results in the suppression of phonon-assisted non-radiative decay. The PL evolution is systematically demonstrated to be controlled by the pressure-regulated exciton–phonon coupling, which can be quantified using Huang–Rhys factor S. Through detailed studies of the S-PLQY relation in a series of 0D hybrid antimony halides, we establish a quantitative structure–property relationship that regulating S value toward 21 leads to the optimized emission. This work not only sheds light on pressure-induced emission in 0D hybrid metal halides but also provides valuable insights into the design principles for enhancing the PLQY in this class of materials.