Sb³⁺-Doped Indium-Based Metal Halide (Gua)₃InCl₆ with Efficient Yellow Emission

In recent years, low-dimensional organic–inorganic hybrid metal halides (OIHMHs) have shown excellent photophysical properties due to their quantum structure, adjustable energy levels, and energy transfer between inorganic and organic components, which have attracted extensive attention from researchers. Herein, we synthesize a zero-dimensional (0D) OIHMH, Sb 3+:(Gua) 3 InCl 6, by introducing Sb 3+ into (Gua) 3 InCl 6, which undergoes a significant enhancement of the emission peak at 580 nm with the photoluminescence quantum yield (PLQY) boosted from 17.86 to 95.72% when excited at 340 nm. This boost in photoluminescence of the doped sample was studied by combining ultrafast femtosecond transient absorption, temperature-dependent photoluminescence (PL) spectra, and density functional theory (DFT) calculation, revealing the process of self-trapped exciton (STE) recombination to emit light at both Sb and In sites in this 0D structure simultaneously. This material with the lowest dark STE level at the In site for emission in the undoped sample can amazingly yield very strong emission in the doped sample, which has never been observed before. Finally, we tested its application in a photoelectric device. This work not only helps to gain a deeper understanding of the formation of STEs in In-based halides but also plays a certain guiding role in the design of new luminescent materials.