Single-particle electroluminescence of CsPbBr 3 perovskite nanocrystals reveals particle-selective recombination and blinking as key efficiency factors

Halide perovskites nanocrystals (NCs) are being explored as promising materials for optoelectronic applications, such as light-emitting devices or lasers. However, electroluminescence devices prepared from such NCs have long suffered from low efficiency and there has been no systematic study on the nanoscale origin of the poor efficiencies. Here, we use single-particle spectroscopy to compare electroluminescence and photoluminescence on the level of individual NCs of the perovskite CsPbBr3. The NCs form aggregates in a conducting matrix used as an emission layer in an electroluminescence device. In electroluminescence, only a small fraction of the NCs within the aggregate is emitting as a result of efficient charge migration, accumulation and selective recombination on larger NCs, leading to pronounced blinking and decreased efficiency. Under the condition of comparable excitation rates in both electroluminescence and photoluminescence, the intrinsic quantum yield in electroluminescence is on average 0.36 of that in photoluminescence. Halide perovskite nanocrystals show high photoluminescence (PL) but their electroluminescence (EL) devices suffered from low external quantum efficiency. Here Sharma et al. study both individual and statistical PL and EL behaviors of these nanocrystals and reveal the origin of the lower EL efficiency.