More Than 9% Efficient ZnSeTe Quantum Dot-Based Blue Electroluminescent Devices

摘要： We explore both synthesis of Cd-free blue quantum dots (QDs) with high-quality photoluminescence (PL) characteristics and fabrication of high-efficiency QD-light-emitting diodes (QLEDs). True blue (445 nm)-emissive, multishelled ZnSeTe QDs with a high PL quantum yield of 84% and sharp bandwidth of 27 nm are prepared. To obtain a better electron transport layer (ETL) material, surface of ZnMgO nanoparticles (NPs) is modified by additional Mg reaction, leading to the possible formation of Mg(OH)2 layer on the surface-modified ZnMgO (m-ZnMgO) NPs. The presence of Mg(OH)2 overlayer, origin for the desirably reduced electron mobility, is supposedly responsible for the improved charge balance of QD emissive layer (EML). The Mg(OH)2 layer is further found to alleviate the emission quenching of QD EML. Combining blue ZnSeTe QDs and m-ZnMgO NP ETL, highly bright, efficient blue QLEDs with the record luminance of 2904 cd/m2 and external quantum efficiency of 9.5% are demonstrated.