Modulating the Carrier Relaxation Dynamics in Heterovalently (Bi3+) Doped CsPbBr3 Nanocrystals

Manipulation of intrinsic carrier relaxation is crucial for designing efficient lead halide perovskite nanocrystal (NC) based optoelectronic devices. The influence of heterovalent Bi3+ doping on the ultrafast carrier dynamics and hot carrier (HC) cooling relaxation of CsPbBr3 NCs has been studied using femtosecond transient absorption spectroscopy and first-principles calculations. The initial HC temperature and LO phonon decay time point to a faster HC relaxation rate in the Bi3+-doped CsPbBr3 NCs. The first-principles calculations disclose the acceleration of carrier relaxation in Bi3+-doped CsPbBr3 NCs due to the appearance of localized bands (antitrap states) within the conduction band. The higher Born effective charges (Z*) and higher soft energetic optical phonon density of states cause higher electron–phonon scattering rates in the Bi-doped CsPbBr3 system, which is responsible for the faster HC cooling rate in doped systems.