Fine Purification Engineering Enables Efficient Perovskite QLEDs with Efficiency Exceeding 23.

Perovskite quantum dots (PeQDs) have great application prospects in fields such as displays and solar cells due to their adjustable band gap, high absorption coefficient, high carrier mobility, and solution processability. However, the ionic crystal characteristic of PeQDs and their surface ligands have led to problems such as solvent sensitivity, poor crystal stability, and difficulty in adjusting the photoelectric properties, which are challenges in high-quality PeQDs. Here, to solve the problem of fluorescence degradation caused by phase change and loss of surface ligands during the purification process of CsPbI 3 QDs, this work develops a purification strategy that finely regulates the polarity of the purification solvent, to obtain high-purity perovskite. This strategy can tune the surface ligand concentration and optoelectronic properties while maintaining the crystal stability. The optimized purification process enables the quantum dots to maintain the same level of luminescence performance as the original solution (PLQY is ∼90%). Meanwhile, the electrical properties are improved to significantly increase the exciton recombination rate under an electrical drive. Finally, a highly efficient QLED with an external quantum efficiency of exceeding 23% can be achieved. This scheme for fine purification of CsPbI 3 QDs will provide some inspiration for the development of efficient PeQDs and the realization of high-performance optoelectronic devices.