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

Lead halide perovskite nanocrystals (NCs) have recently emerged as cutting-edge semiconductor materials for the development of optoelectronic devices. Exploitation of delayed hot carrier (HC) relaxation is an effective way to increase the solar conversion efficiency further. Therefore, delaying the HC relaxation time is essential. Here, we have reported a simple strategy to passivate the surface of CsPbX3 (X = Br/Cl) NCs with hexadecylamine (HDA) molecules, followed by exploitation of the femtosecond transient absorption spectroscopic information to determine the HC relaxation dynamics and ultrafast carrier dynamics. Faster ultrafast carrier relaxation dynamics are observed with the increasing Cl content in the CsPbX3 NCs (X = Br/Cl). Furthermore, we proposed slower ultrafast carrier relaxation dynamics along with longer HC relaxation time in the HDA-passivated CsPbX3 (X = Br/Cl) NCs compared to the pristine NCs. The substantial increase in the initial HC temperature and a prolonged HC decay time additionally reveal the effective delay in HC cooling dynamics after the passivation of the NCs with HDA molecules. A thorough understanding of the charge-carrier relaxation dynamics in CsPbX3 (X = Br/Cl) NCs will provide a way to design efficient optoelectronic devices.