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Highly Efficient Blue–Green Quantum Dot Light-Emitting Diodes Using Stable Low-Cadmium Quaternary-Alloy ZnCdSSe/ZnS Core/Shell Nanocrystals

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journal contribution
posted on 22.05.2013, 00:00 by Huaibin Shen, Sheng Wang, Hongzhe Wang, Jinzhong Niu, Lei Qian, Yixing Yang, Alexandre Titov, Jake Hyvonen, Ying Zheng, Lin Song Li
High-quality blue–green emitting ZnxCd1–xS1–ySey/ZnS core/shell quantum dots (QDs) have been synthesized by a phosphine-free method. The quantum yields of as-synthesized ZnxCd1–xS1–ySey/ZnS core/shell QDs can reach 50–75% with emissions between 450 and 550 nm. The emissions of such core/shell QDs are not susceptible to ligand loss through the photostability test. Blue-green light-emitting diodes (LEDs) based on the low-cadmium ZnxCd1–xS1–ySey/ZnS core/shell QDs have been successfully demonstrated. Composite films of poly­[9,9-dioctylfluorene-co-N-[4-(3-methylpropyl)]-diphenylamine] (TFB) and ZnO nanoparticle layers were chosen as the hole-transporting and the electron-transporting layers, respectively. Highly bright blue–green QD-based light-emitting devices (QD-LEDs) showing maximum luminance up to 10000 cd/m2, in particular, the blue QD-LEDs show an unprecedentedly high brightness over 4700 cd/m2 and peak external quantum efficiency (EQE) of 0.8%, which is the highest value ever reported. These results signify a remarkable progress in QD-LEDs and offer a practicable platform for the realization of QD-based blue–green display and lighting.