Surface co-modification enabling efficient and spectrally stable mixed-halide blue light-emitting diodes.

Using mixed-halide perovskite quantum dots (QDs), with facile spectrum adjustment and extremely high color purity, is one of the most promising ways to achieve blue emission. Nevertheless, the substantial trap states and halide migration-induced phase separation enhance the instability of QDs, which seriously restricts their practical application. To overcome these issues, we creatively develop a strategy for in situ passivation based on a small organic molecule, diphenylphosphorylhydroxylamine (DPH). The strong coordination and hydrogen bonds work in concert to regulate the crystallization process of QDs and saturate vacancy defects to form a ligand-rich surface, thereby achieving more efficient exciton recombination. The resulting QDs are resistant to stronger external stimulation. Thanks to the effective passivation of DPH, the obtained blue PeLEDs with 478 nm emission exhibit extremely high color purity (full width at half maximum of 18 nm) and a maximum external quantum efficiency (EQE) of up to 4.88%. In parallel, the spectrum remains unchanged at an operating voltage of 8 V. This work provides a feasible method for realizing efficient and spectrally stable blue PeLEDs. [ABSTRACT FROM AUTHOR]