A and B sites dual substitution by Na+ and Cu2+ co-doping in CsPbBr3 quantum dots to achieve bright and stable blue light emitting diodes

Light-emitting perovskite quantum dots (PeQDs) are extensively investigated owing to their evident merits. However, it is still a challenge to adjust their intrinsic emissions and enhance their thermal stability to achieve full-color highly emissive QD-based light-emitting diodes (QLEDs), especially blue QLEDs. Herein, we demonstrate an effective strategy to fundamentally stabilize the crystal structure of CsPbBr3 QDs by codoping Na+ and Cu2+ ions, which are designed to substitute Cs+ (A sites) and Pb2+ (B sites), respectively. It is found out that the codoping metal ions have significantly improved the thermal stability and the optical properties of the QDs. 40% of the emission intensity can be remained after 8 thermal cycles (20-120 °C) for CsPbBr3: Na+/Cu2+ QDs, whilst less than 10% is maintained for undoped CsPbBr3 QDs. Accordingly, stable blue QLEDs are packed by CsPbBr3: Na+/Cu2+ QDs. Strong electroluminescence with the maximum luminance of 7161 cd m-2 and low turn-on voltage of 2.4 V are realized. The CIE coordinates are tuned from green (0.10, 0.74) to blue (0.17, 0.25) via Na+ and Cu2+ codoping. The maximum external quantum efficiency (EQEmax) is obtained as 4.52% for PeLEDs based on codoped QDs. The proposed metal ions A and B sites dual substitution strategy guarantees PeQDs as an extremely promising prospect in potential applications as high-resolution displays and high-quality lightings.