Efficient Fully-Solution-Processed Inverted Red Quantum Dot Light-Emitting Diodes Enabled by Charge-Exciton Regulation

Inverted quantum dot light-emitting diodes (QLEDs) show great promise for next-generation displays due to their compatibility with integrated circuit architectures. However, their development has been hindered by inefficient exciton utilization and charge transport imbalance. Here, we present a strategy for regulating charge-exciton dynamics through the rational design of a multifunctional hole transport layer (HTL), incorporating polyethylenimine ethoxylated (PEIE) as a protective interlayer in fully-solution-processed inverted red QLEDs. This HTL comprises poly[(9,9-dioctylfluorenyl-2,7-diyl)-<i>alt</i>-(4,4'-(<i>N</i>-(4-butylphenyl)] (TFB) doped with iridium(III) bis(2-methyldibenzo[<i>f</i>,<i>h</i>]quinoxaline) acetylacetonate (Ir(MDQ)₂(acac)) and performs three critical functions: facilitating Förster resonance energy transfer to quantum dots, enabling Coulomb-assisted hole injection, and suppressing nonradiative recombination. The optimized inverted red QLEDs at a 5 wt % Ir(MDQ)₂(acac) doping concentration achieved a record external quantum efficiency (EQE) of approximately 24.5% and an operational lifetime (<i>T</i>₅₀) exceeding 24,600 h at 100 cd m^-2. This work establishes fundamental design principles for high-performance inverted QLEDs, highlighting the crucial role of charge-exciton management in advancing optoelectronic device performance.