Diversified Synthesis of 0D Hybrid Indium Halides Crystal Structure and PLQY Enhancement via Solvent Environment Regulation and Sb³⁺ Doping

The controllable synthesis of organic–inorganic hybrid metal halide (OIMH) crystal structures remains a challenge in perovskite materials. Achieving identical chemical compositions with distinct crystal structures through precise reaction control enables varied luminescent properties. By adjusting the solution environment while using the same raw materials, this study reports three new 0D hybrid indium-based chlorides named separately as: γ-(HMTA³⁺)InCl₆ (HMTA = hexamethylenetetramine), α-(HMTA³⁺)InCl₆, and (C₇H₁₅N₄⁺)[InCl₄(DMSO)₂] (DMSO = dimethylsulfoxide). Sb³⁺ doping significantly broadens the excitation band of these materials. Under UV excitation, the doped compounds exhibit bright self-trapped exciton emissions with different colors, enhanced photoluminescence quantum yield of 26.96%, 68.94%, and 89.97%. The symmetry of Indium octahedra is modulated by crystal symmetry, with the high symmetry of γ-(HMTA³⁺)InCl₆ and α-(HMTA³⁺)InCl₆ attributed to the quasi-spherical HTMA³⁺ unit. Furthermore, the [InCl₄(DMSO)₂]⁻ octahedral coordination ion, reported for the first time in (C₇H₁₅N₄⁺)[InCl₄(DMSO)₂], exhibits greater distortions than common (InCl₆)³⁻ octahedra, which alters the electronic structure of VBM orbitals and broadens the PL excitation band. Additionally, γ-(HMTA³⁺)InCl₆ exhibits excitation-dependent emission and white light emission potential at low Sb³⁺ doping concentrations, arising from the excited-state energy transfer between different STE energy levels. This study advances the structural design and luminescence modulation of OIMHs, offering insights for future photophysical applications.