Realizing Near-Unity Photoluminescence Efficiency\nin Antimony-Doped Indium-Based Halides Induced by Strong Electron–Phonon\nCoupling

Exploring\na zero-dimensional (0D) hybrid halide with a large Stokes\nshift and efficient broad-band emission is highly desirable due to\nits enormous potential for solid-state lighting (SSL) application.\nHowever, it is still challenging to develop a highly emissive 0D hybrid\nhalide with low toxicity and remarkable stability. Herein, we developed\na novel indium-based metal halide A<sub>5</sub>In<sub>2</sub>Cl<sub>16</sub>·4H<sub>2</sub>O (A = doubly protonated 1,4-diaminobutane)\nwhose inorganic octahedrons are completely isolated by the organic\ncations to form the 0D structure. Experimental and theoretical studies\nconfirmed that Sb-doped A<sub>5</sub>In<sub>2</sub>Cl<sub>16</sub>·4H<sub>2</sub>O exhibits broad yellow emission with a photoluminescence\nquantum yield (PLQY) of up to 98%. The intense yellow emission can\nbe attributed to the radiative recombination of triplet self-trapped\nexcitons (STEs) in [SbCl<sub>6</sub>]<sup>3–</sup> octahedrons\ncaused by the strong electron–phonon coupling. Benefiting from\nthe excellent stability and photoluminescence performance, A<sub>5</sub>In<sub>2</sub>Cl<sub>16</sub>·4H<sub>2</sub>O:15%Sb was used\nas the yellow phosphor to prepare a white-light-emitting diode (WLED)\ndevice with a color rendering index of 87.8 and a luminous efficiency\nof up to 36.18 lm/W, demonstrating its potential in SSL applications.\nThis work provides a guidance for developing environmentally friendly,\nefficient, and stable ultraviolet (UV)-excited broad-band emission\nmaterials.