Localized exciton emission in CsPbBr3 nanocrystals synthesized with excess bromide ions

All-inorganic perovskite nanocrystals (NCs) have recently emerged as a new class of materials due to their tunable bandgaps and high photoluminescence quantum yields (PLQYs). The origin of the enhancement of PLQY of CsPbBr3 NCs is usually attributed to the efficient passivation of the surface halide vacancies creating nonradiative recombination sites. In this work, Br-rich CsPbBr3 NCs with a PLQY of 97% were prepared using an extreme excess of Br source with Br/Pb of 4.5/1 from the ligand itself at room temperature. Br-rich CsPbBr3 NC based light-emitting devices were fabricated under ambient conditions, exhibiting the maximum current efficiency of 1 cd A−1 at the luminance of 750 cd m−2. First principles calculations indicate that Br interstitials can form the strong localized states. Such localized effect can prevent photogenerated carriers from defusing to non-radiative recombination centers, thus being responsible for the high emission efficiency.