Stable and efficient quantum-dot light-emitting diodes based on solution-processed multilayer structures

Multilayer, colloidal quantum-dot based light-emitting diodes that exhibit high brightness, solution processability, colour tunability and narrow emission bandwidth are reported. These devices consist of a quantum-dot emissive layer sandwiched between an organic hole transport layer and an electron transport layer of ZnO nanoparticles, all of which are deposited using a solution process. The devices have maximum luminance and power efficiency values of 4,200 cd m(-2) and 0.17 lm W-1 for blue emission, 68,000 cd m(-2) and 8.2 lm W-1 for green, and 31,000 cd m(-2) and 3.8 lm W-1 for orange-red. Moreover, with the incorporation of the ZnO nanoparticles, these devices exhibit high environmental stability, and the unencapsulated devices have operating lifetimes exceeding 250 h in low vacuum with an initial brightness of 600 cd m(-2).