Structure and Photophysical Properties of Cubic-Shaped Cadmium(II)-Doped CsPbBr₃ 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 CsPb_1-xCd_xBr₃ NCs with a varied amount (3, 8, and 15%) of Cd(II) doping are explored. The incorporation of the increasing amount of Cd²⁺ 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 CsPb_1-xCd_xBr₃ NCs along with an almost threefold increase in the hot carrier temperature, which indicates more efficient population of the band edge compared to pristine CsPbBr₃. Furthermore, it is demonstrated that CsPb_1-xCd_xBr₃ NCs exhibit their own volume scaling law for the exciton-exciton annihilation threshold and rate. Specifically, Cd(II)-doped CsPbBr₃ NCs with a smaller size exhibit a higher Auger threshold than the larger pristine CsPbBr₃ NCs, which makes them potentially useful for light-emitting and lasing applications. The insights gained into the excited carrier dynamics in CsPb_1-xCd_xBr₃ NCs open new pathways for the development of efficient nanoscale emitters in the blue spectral range.