Cesium Azide—An Efficient Material for Green Light-Emitting Diodes With Giant Quantum Dots

A novel efficient and air-stable electron injection layer (EIL) of cesium azide (CsN3) was compared with conventional ones including CsF, Cs2CO3, LiF and without EIL in type-II quantum dot light-emitting diodes (QLEDs) with both organic electron and hole transport layers. Via directly decomposing to pristine cesium (Cs), the low-temperature evaporated CsN3 provided a better interfacial energy level alignment without damaging the underneath organic layer. Consequently, the current efficiencies of 7.45 cd/A was achieved in the CsN3-based green QLEDs consisting of giant CdSe@ZnS/ZnS quantum dots at 544 nm, which was 310% (at 10 mA/cm2) improvement over the LiF-based QLEDs. Moreover, the light turn-on voltage in CsN3-devices significantly decreased $\sim 5.5$ V in comparison with LiF-devices.