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 the STE states and ground states (GSs) results in the suppression of phonon-assisted non-radiative decay. The photoluminescence (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.