ZnSe:Te/ZnSeS/ZnS Nanocrystals: An Access to Cadmium-Free Pure-Blue Quantum-Dot Light-Emitting Diodes

摘要： Cadmium-free quantum dots (QDs) are attracting considerable research attention because of their low toxicity. However, the bandgap of most cadmium-free QDs avoids the pure-blue region, which confers difficulty in realizing pure-blue quantum-dot light-emitting diodes (QLEDs). In this work, we successfully tuned the emission wavelength of ZnSe/ZnS quantum dots from the violet region (~ 420 nm) to the pure-blue region (450 – 460 nm) by doping Te into the ZnSe core. The ZnSe:0.03Te/ZnSeS/ZnS QDs sample with an emission position of 450 nm and quantum yield of 30% was the most balanced formula. To overcome the energy gap between the hole-transfer layer and QD layers, a specific hole-transfer layer was developed for normal-structure QLEDs. Such structure QLED by ZnSe:0.03Te/ZnSeS/ZnS QDs achieved the pure-blue light emission at 455 nm, a low turn-on voltage of 4.4 V, and external quantum efficiency of 0.33%. Overall, our cadmium-free QLED achieved pure-blue emission, revealing the potential of ZnSe-based pure-blue QLEDs for future displays.