Mixed halide perovskite nanocrystals with surface engineering based on pseudohalide passivation and Short-Chain ligand exchange for High-Performance blue Light-Emitting diodes

Perovskite nanocrystals (PeNCs) have attracted considerable interest in light-emitting diodes (LEDs) owing to their unique optoelectronic properties. Although significant progress has been made in green and red perovskite LEDs (PeLEDs) with PeNCs, the performance of blue PeLEDs is still limited. The main obstacles for blue PeLEDs based on PeNCs are their Cl vacancy-induced low quantum efficiency in mixed halide (Br/Cl) systems and high electrical resistance from long organic capping ligands. In this study, to overcome these issues and achieve high-performance blue PeLEDs, a surface engineering (SE) strategy based on pseudohalide defect passivation and short-chain ligand exchange was introduced. By passivating Cl vacancies with SCN^– and exchanging long-chain oleic acid and oleylamine ligands with short octylphosphonic acid and 3,3-diphenylpropyl amine, respectively, the optoelectronic properties of the PeNCs were significantly enhanced. The blue PeLEDs based on PeNCs, using SE, exhibited a maximum luminance of 1874 cd/m² and maximum external quantum efficiency of 4.9 % at an electroluminescence wavelength of 467 nm, which satisfies the blue primary color requirement (467 nm) in Rec. 2020 color space.