High-Efficiency Cadmium-Free Blue Quantum Dot Light-Emitting Diodes Enabled by Engineering of a Hole Transporting Interface with a Multifunctional Molecule

High-performance blue quantum dot light-emitting diodes (QLEDs) have great potential application in full-color display. However, realization of eco-friendly pure-blue QLEDs is limited by the shallow highest occupied molecular orbital (HOMO) level and low conductivity of hole transport layers (HTLs). Here, a facile strategy of doping the HTL with a multifunctional molecule, i.e., silver bis(trifluoromethylsulfonyl)imide (Ag-TFSI), is demonstrated. This p-doping strategy simultaneously improves the energy level alignment at the HTL/QD interface and enhances the conductivity of the HTL, as well as prevents quantum dots (QDs) from getting charged. Benefiting from the better charge balance and mitigated nonradiative recombination of excitons, the blue zinc tellurium selenium (ZnTeSe)-based QLEDs exhibit a peak external quantum efficiency (EQE) of 13.9% with an electroluminance emission located at 456 nm. Moreover, the device lifetime is enhanced by more than twofold. This work suggests a promising p-doping strategy to accelerate the development of eco-friendly QLEDs toward display applications.