Pressure-triggered intense natural white emission via controllable distortions of antimony chloride dimers.

• Delicate distortions of [Sb 2 Cl 10 ]4− dimers dramatically promote self-trapped exciton emission. • Varied emission equilibrium of triplet excitons induces intense natural white emission. • Underlying Mechanisms determining dimeric self-trapped emission are analyzed. • High pressure is proposed to optimize photoluminescence properties of metal-halogen dimers. Zero-dimensional (0D) hybrid metal halides (HMHs), featured with unique self-trapped exciton (STE) emissions, are emerging photoluminescence (PL) materials for photoelectronic applications. Compared with metal-halogen monomers, dimeric units in 0D HMHs possess more structural flexibility and less spatial confinement of excitons, creating new opportunities for PL engineering. Herein, high pressure is employed on 0D (C 3 H 12 N 2) 2 Sb 2 Cl 10 to controllably distort inter- and intra-octahedral structures within [Sb 2 Cl 10 ]4− dimers. Intense natural white emission is achieved with dramatically increased photoluminescence quantum yield from less than ≈1% to 74.2 %. The high-pressure emission of (C 3 H 12 N 2) 2 Sb 2 Cl 10 is proven to originate from the STE recombination from triplet states with varied emission equilibrium, as well as the promoted excitonic trapping with restrained nonradiative recombination. This work offers valuable insights into the structure effects on STE emission and the transition mechanisms of metal-halogen dimers, which are crucial for developing novel metal halides for illumination. [ABSTRACT FROM AUTHOR]