Solution-Processed Double-Junction Quantum-Dot Light-Emitting Diodes with EQE of Over 40.

Despite the fast development made in quantum-dot (QD) light-emitting diodes (QD-LEDs) with single-junction, it remains a big challenge for making tandem QD-LEDs with high-performance. Here, we report solution-processed double-junction tandem QD-LEDs with a high external quantum efficiency of 42.2% and a high current efficiency of 183.3 cd A-1, which are comparable to those of the best vacuum-deposited tandem organic LEDs (OLEDs). Such high-efficiency devices are achieved by interface engineering of fully optimized single light-emitting units which improves carriers transport/injection balance and suppresses exciton quenching induced by ZnO and design of an effective interconnecting layer (ICL) consisting of poly(4-butylphenyl-diphenyl-amine) (poly-TPD) mixed poly(9-vinlycarbazole) (PVK)/PEDOT:PSS/polyethylenimine ethoxylated (PEIE) modified ZnO.