Stable and Strong Emission CsPbBr3 Quantum Dots by Surface Engineering for High-Performance Optoelectronic Films

We demonstrated complete surface passivation of CsPbBr3 quantum dots (QDs) by treatment with di-dodecyldimethylammonium bromide (DDAB) and sodium thiocyanate (NaSCN), resulting in dispersions with photostable photoluminescence of near-unity quantum yield (∼100%) as well as high carrier mobility of QDs' film. Br- from DDAB and SCN- from NaSCN passivated the bromine vacancies of the QDs to reduce the surface defect density and increase the stability. The QDs-passivated maintained the original photoluminescence intensity under ultraviolet irradiation from a 150 W xenon lamp for 1 h, whereas the PL intensity of QDs-control dropped quickly to 20% of its initial value. The shorter DDA+ ligands also improved carrier transport in the QDs-passivated film, which was verified by conductivity and space charge limited current measurements. When used as the photoemitting species in a solution-processed light-emitting diode structure, the surface treatment increased the maximum luminance from 550 to 1200 cd·m-2 and reduced the turn-on voltage from 3.1 to 2.8 V.