Efficient Yellow Emission and Near-Unified Photoluminescence Quantum Yield of Sb³⁺ in a One-Dimensional Confinement Cadmium Chloride Lattice

Sb 3+, with a 5s 2 electron configuration, has been widely studied as a dopant for its efficient self-trapped exciton (STE) broadband emission. However, the efficient emission of Sb 3+ -doped one-dimensional (1D) structures and the energy/charge transfer between the host and dopant are rarely reported. In this paper, a series of Sb 3+ -doped 1D (TDMP)CdCl 4 (TDMP = trans -2,5-dimethylpiperazine) powder crystals were prepared by the solvothermal method. The 1D quantum confinement effect and Jahn–Teller distortion in this organic–inorganic hybrid with a soft lattice generate strong electron–phonon coupling. In addition, we also found a fast energy transfer process between the host ([CdCl 6 ] 2– ) and the dopant ([SbCl 6 ] 3– ). The synergy of strong electron–phonon coupling and fast energy transfer enables 8.8% Sb 3+:(TDMP)CdCl 4 to exhibit efficient broadband yellow emission under UV excitation with a photoluminescence quantum yield (PLQY) of 99.69%. DFT calculations indicate that the emission comes from the triplet self-trapped excitons (STEs) emission of the [SbCl 6 ] 3– octahedron. This work provides a deeper understanding of the emission of Sb 3+ in doped systems and provides a strategy to guide the design of future efficient luminescent materials.