Exploring the Carrier Dynamics in Zinc Oxide–Metal Halide-Based Perovskite Nanostructures: Toward Reduced Dielectric Loss and Improved Photocurrent

Metal halide-based perovskites have emerged as a potential candidate for optoelectronic applications because of their impressive performance achieved by tuning the optical/electrical properties through tailoring the perovskite nanostructures. Herein, we report the synthesis of composite nanostructures by incorporation of ZnO (∼6 nm) into the CsPbBr3 (CPB) perovskite framework, which shows significant enhancement of photocurrent because of efficient interfacial charge separation and reduced dielectric loss. Detailed steady-state and time-resolved photoluminescence studies have been carried out to understand charge transfer dynamics in the CsPbBr3/ZnO nanostructure composite system. Femtosecond transient absorption and broadband dielectric spectroscopy studies were carried out to determine the charge carrier relaxation and transfer mechanism. The redox energy-level diagram suggests that the photoexcited electron from the conduction band (CB) of CPB can be transferred to the CB of ZnO NP because of thermodynamic viability. Ultrafast studies reveal that the electron transfer takes place from the perovskite nanostructures to ZnO NP within ∼500 fs and limits the recombination process by efficient charge separation and charge accumulation at the interfaces. Dielectric studies also reveal reduced charge leakage in composite nanostructures with efficient charge separation by facilitating the charge accumulation at the interfaces. Overall, the efficient charge transfer and slow carrier recombination with reduced dielectric losses significantly improved the photocurrent behavior in the CsPbBr3/ZnO nanostructure composite system as desired for optoelectronic devices.