The efficient green light-emitting diodes based on low-toxicity Zr-Pb alloy perovskite quantum dots passivated by inorganic ligand

Perovskite quantum dots (PeQDs) are emerging as one of the most promising candidates for next-generation display technology due to their outstanding optical and electrical properties. However, the inherent instability, lead-toxicity and poor electrical conductivity of PeQDs films have seriously hindered their commercial applications. To solve these problems, we adopted the strategy of Zr ions doping and in-situ passivation of CsPbBr3 PeQDs with the short-chain inorganic ligand potassium thiocyanate (KSCN), which not only enhanced the stability and boosted the photoluminescence quantum yield (PLQY) of PeQDs films, but also improved their electrical conductivity. To further solve the problem of charge injection balance and improve the operating lifetime of the devices, we simultaneously used all-inorganic metal oxide semiconductor materials Mg-doped ZnO (Mg-ZnO) and Mg-doped NiOx (Mg-NiOx) as the electron and hole transport layers of QLEDs (ETL and HTL), respectively. The operating stability of the devices was greatly improved while being able to withstand higher current densities. Therefore, using Zr-doped and KSCN passivated CsPbBr3 (Zr doped CsPbBr3-KSCN) PeQDs as the light-emitting layer, we fabricated highly efficient and stable green-light all-inorganic quantum dots light-emitting diodes (QLEDs) with the maximum external quantum efficiency (EQE) of 13.8% and the maximum brightness of 24800 cd/m2. These green perovskite QLEDs provide a working half-life of 360 min (initial brightness is 1000 cd/m2) and the operating half-life of the devices is more than two times higher than that of the reference devices. Our proposed strategy based on doping and in-situ inorganic ligand passivation will open a new avenue for fabricating efficient, stable and other colored perovskite QLEDs.