Structure and Photophysical Properties of Cubic-Shaped Cadmium(II)-Doped CsPbBr Perovskite Nanocrystals.

Bandgap engineering in lead halide perovskites through the lead-site doping is a promising strategy to achieve blue-shifted emission in nanocrystals (NCs) without relying on quantum confinement or halide mixing. Here, the structure and photophysical properties of CsPbCdBr NCs with a varied amount (3, 8, and 15%) of Cd(II) doping are explored. The incorporation of the increasing amount of Cd ions results in an up to 5 nm decrease of the average NC size, while the emission is blue-shifted from 515 to 485 nm. Applying the ultrafast transient absorption spectroscopy, a significant enhancement is observed in the absorption oscillator strength of CsPbCdBr NCs along with an almost threefold increase in the hot carrier temperature, which indicates more efficient population of the band edge compared to pristine CsPbBr. Furthermore, it is demonstrated that CsPbCdBr NCs exhibit their own volume scaling law for the exciton-exciton annihilation threshold and rate. Specifically, Cd(II)-doped CsPbBr NCs with a smaller size exhibit a higher Auger threshold than the larger pristine CsPbBr NCs, which makes them potentially useful for light-emitting and lasing applications. The insights gained into the excited carrier dynamics in CsPbCdBr NCs open new pathways for the development of efficient nanoscale emitters in the blue spectral range.