Universal surface tailoring of perovskite nanocrystals via organic pseudohalide ligands applicable to green and blue light-emitting diodes

Proper management of surface defects in perovskite nanocrystals (PeNCs) has resulted in near-unity photoluminescence quantum yield and the development of high-performance light-emitting diodes (LEDs). However, most PeNCs still suffer from incomplete surface passivation, which results in non-ideal efficiencies. Herein, we devise a simple surface tailoring of CsPbBr3 NCs with organic pseudohalide ligands, didodecyldimethylammonium tetrafluoroborate (DDA-BF4). Results suggest that the DDA cation and BF4 anion simultaneously coordinated on the CsPbBr3 NC surfaces, thereby dramatically improving optical properties and colloidal stability. With this passivation, surface-tailored CsPbBr3 NCs were applied to green LEDs, which showed significantly higher external quantum efficiencies than LEDs with untreated PeNCs and stable electroluminescence (EL) at a wavelength of 516 nm. Also, when this method was applied to sky-blue LED based on CsPbBr3-xClx NCs (EL at 484 nm), similar improvement in device performance was observed. We believe that organic pseudohalide treatment provides a universal methodology that can be applicable to green and blue PeNC-based LEDs, providing a promising platform for future displays and lighting technologies.