Realizing Near-Unity Photoluminescence Efficiency in Antimony-Doped Indium-Based Halides Induced by Strong Electron–Phonon Coupling

Exploring a zero-dimensional (0D) hybrid halide with a large Stokes shift and efficient broad-band emission is highly desirable due to its enormous potential for solid-state lighting (SSL) application. However, it is still challenging to develop a highly emissive 0D hybrid halide with low toxicity and remarkable stability. Herein, we developed a novel indium-based metal halide A5In2Cl16·4H2O (A = doubly protonated 1,4-diaminobutane) whose inorganic octahedrons are completely isolated by the organic cations to form the 0D structure. Experimental and theoretical studies confirmed that Sb-doped A5In2Cl16·4H2O exhibits broad yellow emission with a photoluminescence quantum yield (PLQY) of up to 98%. The intense yellow emission can be attributed to the radiative recombination of triplet self-trapped excitons (STEs) in [SbCl6]3– octahedrons caused by the strong electron–phonon coupling. Benefiting from the excellent stability and photoluminescence performance, A5In2Cl16·4H2O:15%Sb was used as the yellow phosphor to prepare a white-light-emitting diode (WLED) device with a color rendering index of 87.8 and a luminous efficiency of up to 36.18 lm/W, demonstrating its potential in SSL applications. This work provides a guidance for developing environmentally friendly, efficient, and stable ultraviolet (UV)-excited broad-band emission materials.