Slowing Down the Hot Carrier Relaxation Dynamics of CsPbX3 Nanocrystals by the Surface Passivation Strategy

Lead halide perovskite nanocrystals (NCs) have recentlyemergedas cutting-edge semiconductor materials for the development of optoelectronicdevices. Exploitation of delayed hot carrier (HC) relaxation is aneffective way to increase the solar conversion efficiency further.Therefore, delaying the HC relaxation time is essential. Here, wehave reported a simple strategy to passivate the surface of CsPbX3 (X = Br/Cl) NCs with hexadecylamine (HDA) molecules, followedby exploitation of the femtosecond transient absorption spectroscopicinformation to determine the HC relaxation dynamics and ultrafastcarrier dynamics. Faster ultrafast carrier relaxation dynamics areobserved with the increasing Cl content in the CsPbX3 NCs(X = Br/Cl). Furthermore, we proposed slower ultrafast carrier relaxationdynamics along with longer HC relaxation time in the HDA-passivatedCsPbX(3) (X = Br/Cl) NCs compared to the pristine NCs. Thesubstantial increase in the initial HC temperature and a prolongedHC decay time additionally reveal the effective delay in HC coolingdynamics after the passivation of the NCs with HDA molecules. A thoroughunderstanding of the charge-carrier relaxation dynamics in CsPbX3 (X = Br/Cl) NCs will provide a way to design efficient optoelectronicdevices.