High-Efficiency and Long-Lifetime Red Quantum-Dot LEDs Enabled by a Polymer-TADF-Emitter-Based Hole Transport Layer.

Quantum-dot light-emitting diodes (QLEDs) are regarded as promising options for various optoelectronic applications. However, they struggle with an excessive injection of electrons relative to holes, constraining their performance. Here, we propose an efficient hole transport layer (HTL) sensitization method that can reuse leaked electrons and raise the hole transport capability to tackle this challenge. The HTL consists of poly(9-vinylcarbazole) (PVK) mixed with a light-blue thermally activated delayed fluorescence emitter, 2-(3,5-bis(trifluoromethyl)phenyl)-5-(2,3,4,5,6-penta(9-carbazol-9-yl)phenyl)-1,3,4-oxadiazole (dCF5CzOXD). The resulting red QLEDs at a mixing concentration of 25 wt % simultaneously yield a highest current efficiency/external quantum efficiency (EQE) of 42.3 cd A/35.8%, and an extended lifetime exceeding 81,408 h at 100 cd m, positioning them among the most efficient and stable QLEDs reported to date. Remarkably, a consistent EQE value exceeding 32.0% is maintained across a broad luminance range of 9000 to 200,000 cd m.