Efficient CsPbBr3 nanocrystals light emitting diodes achieved with Na+ modifying

Abstract CsPbBr3 nanocrystals (NCs) with enhanced photoluminescence quantum yield (PLQY) and stability have been regarded as promising emissive materials in flexible, low-cost, and high-definition display applications. The long-chain organic ligands, i.e. oleylamine and oleic acid, are essential to stabilize the NCs and increase their PLQY, but the long-chain ligands show detrimental effects on the charge transport ability of the resultant NCs, which deteriorate the performance of light emitting diodes (LEDs). Here, we introduced Na+ ions during the synthesis of perovskite NCs. Because of strong ionic bonding between Na+ and Br− ions, the introduced Na+ ions could stabilize the Br− ions hanged on the surface, which is beneficial to suppressing the generation of Br− vacancies. In addition, when the Na+ ions were capped on perovskite surface, the amount of long-chain organic ligands on the surface of perovskite NCs were reduced. As a result, high-quality perovskite NCs with uniform microstructure, high PLQY of 84.6%, and improved charge transport ability are achieved with appropriate addition of Na+ ions, which enables us increase the EQE of a LED device from 5.59% to 7.33%.