Efficient deep-blue LEDs based on colloidal CsPbBr₃ nanoplatelets meeting the Rec.2020 standard

Colloidally quantum-confined CsPbBr₃ nanoplatelets (NPLs) exhibit narrow emission linewidths and thickness-tunable photoluminescence, making them ideal candidates for deep-blue perovskite light-emitting diodes (PeLEDs). However, the weak surface coordination of conventional long-chain ligands (e.g., oleylamine and oleic acid) leads to face-to-face stacking of the NPLs, resulting in undesirable emission redshifts in their PeLEDs. Herein, we report an efficient deep-blue PeLED based on colloidal CsPbBr₃ NPLs that meet the Rec.2020 color standard, enabled by an acid-assisted ligand passivation strategy. Surface chemical analysis reveals that hydrobromic acid facilitates proton-assisted stripping of the long-chain ligands, followed by the formation of stable Pb-S-P coordination bonds with thio-tributylphosphine, which exhibits a high adsorption energy (E_ads = -1.13 eV). This approach significantly improves surface defect passivation, yielding a photoluminescence quantum yield of 96% and a narrow 13 nm full-width-at-half-maximum deep-blue emission. Enhanced exciton recombination and reduced defect state density are evidenced by a prolonged photoluminescence lifetime and slower absorption bleach recovery kinetics. The resulting PeLEDs achieve record-breaking performance among CsPbBr₃ NPL-based systems, with a maximum external quantum efficiency of 6.81% at 461 nm, a peak luminance of 143 cd m^-2, and the CIE color coordinates (CIE-y = 0.046) that comply with Rec.2020 standards. This work presents an effective strategy for developing efficient and stable deep-blue perovskite emitters, demonstrating significant potential for the commercialization of perovskite nanomaterials in next-generation ultra-high-definition displays.