Dual-Function Hole Injection Layer Created via p-Type Doping for High-Performance InP-Based Quantum-Dot Light-Emitting Diode

This paper proposes a doping-based strategy to fabricate dual-functional hole injection layers (HILs) for high-performance quantum-dot light-emitting diodes (QLEDs). Specifically, the HIL is created by introducing a p-type dopant, 4-isopropyl-4′-methyldiphenyliodonium tetrakis(pentafluorophenyl)borate (TPFB), into N4,N4′-Di(naphthalen-1-yl)-N4,N4′-bis(4-vinylphenyl) biphenyl-4,4′-diamine (VNPB), the host material. Due to its strong electron-accepting character, TPFB promotes efficient hole injection, while the vinyl groups in VNPB enable the formation of robust crosslinked thin films upon thermal annealing. Furthermore, through precise control of the doping concentration, the HIL's highest occupied molecular orbital level can be tuned, which lowers the hole injection barrier effectively; simultaneously, the robust crosslinked network structure substantially suppresses leakage current. Consequently, InP-based red QLEDs incorporating the proposed HIL exhibit enhanced external quantum efficiency and operational stability compared with conventional devices employing poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid). This dual-function HIL strategy simultaneously addresses hole injection and solvent resistance issues, offering a promising route toward high-efficiency QLEDs with minimal leakage current.