Sb-doped 0D CsGdCl microcrystals with a near-unity photoluminescence quantum yield and high thermal quenching resistance for light-emitting application

All-inorganic lead-free luminescent metal halides doped with main-group ns 2 -electron ions have attracted considerable interest in a variety of optoelectronic applications. However, they normally suffer from severe thermal quenching of photoluminescence (PL) due to aggravated nonradiative relaxation at high temperatures. Herein, we report a new class of luminescent materials based on 5s 2 -electron Sb 3+ -doped 0D Cs 3 GdCl 6 microcrystals (MCs), which exhibit intense yellowish PL at 540 nm under ultraviolet (UV) excitation, in parallel with a broad bandwidth of 510 meV, a large Stokes shift of 190 nm, a near-unity PL quantum yield, and remarkable resistance against thermal quenching ( I 150°C = 82.4%). Mechanistic investigation unravels that the broadband emission originates from the spin-orbital allowed 3 P 1 → 1 S 0 transition of Sb 3+ which experiences a dynamic Jahn-Teller distortion in the excited state. These properties facilitate Cs 3 GdCl 6 :Sb 3+ MCs as an efficient yellowish phosphor for near-UV-converted white light-emitting diodes, demonstrating a high color-rendering index of 96.4 and excellent operational stability. This work provides not only fundamental insights into the excited-state dynamics of Sb 3+ in Cs 3 GdCl 6 MCs, but also a new way for the exploration of novel and highly emissive rare-earth halides through ns 2 -electron ion doping towards various light-emitting applications. A new class of luminescent materials based on Sb 3+ -doped 0D Cs 3 GdCl 6 microcrystals featuring a near-unity quantum yield (QY) and good thermal quenching resistance ( I 150°C = 82.4%) are developed and explored for white light-emitting diodes.