Organic Tellurium (IV) Halide Hybrid as an Efficient Phosphor for Hybrid Light-Emitting Diodes

Developing stable and environmentally friendly metal halide electroluminescent materials is highly desirable. Lead-free hybrids with ns² electron configurations offer high stability and efficient self-trapped exciton (STE) emission but suffer from poor carrier transport in devices. Furthermore, most of them are incompatible with host materials, leading to inefficient energy transfer and inferior device performance. Herein, a Te-based hybrid material, (PPh₃Bu)₂TeCl₆, is elaborately synthesized which demonstrates a strong absorption band beyond 400 nm and bright orange emission peaked at 605 nm, with a photoluminescence quantum yield (PLQY) of 24% and a lifetime of 6.5 µs. Solution-processed hybrid LEDs with neat (PPh₃Bu)₂TeCl₆ as an emitter exhibit dual emissions, achieving current efficiency (CE) of 0.67 cd A⁻¹ and external quantum efficiency (EQE) of 0.34%. Inspiritingly, once (PPh₃Bu)₂TeCl₆ is blended with host materials to serve as a light-emitting layer, the CE and EQE of the hybrid LEDs are dramatically increased to 8.1 cd A⁻¹ and 4.3%, respectively. Notably, the device efficiency of (PPh₃Bu)₂TeCl₆ is more than twice that of (PPh₃Bu)₂SbCl₅, despite its PLQY being only one-third that of (PPh₃Bu)₂SbCl₅, thus highlighting the much superior electroluminescence of (PPh₃Bu)₂TeCl₆ due to the more facile energy transfer from host materials. Anyway, this work pioneers the use of Te-based light-emitting materials for electroluminescent devices.