Highly Efficient Blue Perovskite Quantum Dots Light-Emitting Diodes Based on Ligand-Assisted Anion Exchange Method

High-performance blue perovskite quantum dots (PQDs) are of key importance for electroluminescent light-emitting diodes (LEDs) toward full color display in the future. Here, mixed halogen PQDs CsPb(Br x /Cl 1– x ) 3 with a tunable emission wavelength was obtained through a strategy of ligand-assisted anion exchange assisted by didodecydimethyammonium chloride (DDAC) ligand. Surface Br – vacancies of the PQD are passivated by the halogen atoms in the anchored DDAC ligand, enabling a high efficiency emission of blue light from the PQD. Stable anchoring of the ligand also improves the robustness of the PQD during its purification in weak polar solvents. Well-controlled chlorine stoichiometry of the PQD also allows fine-tuning of its photoluminescence and electroluminescence spectra in the range of 424–514 nm and 453–500 nm. The external quantum efficiency of the fabricated PQDs LED device reaches 10.1% at 495 nm, 6.5% at 484 nm, and 5.1% at 470 nm (NTSC pure blue) under a constant current test. Our work provides a facile method without additional purification or ligand separation to achieve highly efficient blue PQDs with a tunable emission wavelength, promoting the advance of blue PQDs LED.