Insight into Hot Carrier Kinetics of CsPbBr₃/ZnO Heterostructures for Photodetector Application

Understanding the hot carrier kinetics in heterostructures of inorganic halide perovskite nanocrystals (PNCs) and extraction of the excess energy of hot-carriers is crucial for their future emergence in optoelectronic devices. Herein, CsPbBr3/ZnO heterostructures have been prepared via the most adopted in situ hot-injection method, and ZnO nanoparticles were obtained by a simple chemical process. We have investigated the carrier transfer dynamics through steady-state and ultrafast optical measurements. Steady-state measurements (i.e., photoluminescence and time-resolved photoluminescence decay) reveal that electron transfer from PNCs to surface-attached ZnO nanoparticles is the most probable transition process that happened in heterostructured systems. Furthermore, deep insights into the charge transfer kinetics were investigated by performing ultrafast transient absorption (UTA) spectroscopy at two varying pump fluences (i.e., 0.40 and 0.20 mW) with an excitation wavelength of 450 nm. UTA analysis reveals a significant slow hot carrier cooling at 0.40 mW fluence (from 670 fs to 1.56 ps) and 0.20 mW (from 480 fs to 1.23 ps) in CsPbBr3/ZnO heterostructure systems, suggesting reduced exciton recombination and high charge-carrier transfer through the heterostructure interface. The efficient charge extraction in CsPbBr3/ZnO results in a measurable change in photodetector responsivity and detectivity. This study provides an understanding of the hot carrier kinetics of metal halide perovskites CsPbBr3/ZnO for optoelectronic device applications.