Zero‐dimensional (0D) organic–inorganic hybrid metal halides (OIMHs) are promising broadband emitters due to their large Stokes shift; however, achieving high photoluminescence quantum yield (PLQY) in indium‐based systems remains challenging. A systematic matrix‐engineering approach is implemented in a family of indium chlorides and bromides, incorporating protonated ethylenediamine (en), diethylenetriamine (dien), and tris(2‐aminoethyl)amine (tren) cations. Structural characterization reveals isolated InX 6 3− and InCl 5 (H 2 O) 2− units (X = Cl, Br) with varying site symmetry and distortion. Antimony doping (Sb 3+ ) activates broadband photoluminescence from the 3 P 1 → 1 S 0 electronic transition, with PLQY being strongly dependent on the host symmetry and composition. Near‐unity PLQY is achieved at low (0.5%) Sb 3+ content in (dien)InCl 6 :Sb 3+ , while the centrosymmetric (en) 2 InCl 7 ·H 2 O:Sb 3+ polymorph exhibits higher efficiency than its noncentrosymmetric analog (en)InCl 5 ·H 2 O:Sb 3+ . Systematic blueshift in emission with increasing organic cation size occurs without a monotonic change in the bandgap, indicating that Stokes shift in these compounds is governed by both fundamental electronic structure and local coordination environment. These results demonstrate that synergistic control of the host structure and dopant concentration govern radiative efficiency in indium‐based OIMHs.
Valueva et al. (Fri,) studied this question.