Unraveling the Microscopic Origin of Photoconductivity Enhancement in CsPbBr3 Quantum Dot-Passivated Hybrid Perovskites by Optical Pump-Terahertz Probe Spectroscopy

We investigate the microscopic origin of the enhanced photoconductivity and charge carrier transport in a mixed-cation, mixed-halide hybrid perovskite passivated with CsPbBr3 quantum dots using optical pump-terahertz probe spectroscopy. We directly access the complex transient photoconductivity in the terahertz range, whose analysis allows us to elucidate the effect of CsPbBr3 quantum dot passivation on charge carrier transport between crystalline domains. We find that, for the passivated perovskites, transport properties are significantly improved, with the Drude–Smith backscattering parameter changing from −0.60 to −0.42, corresponding to a 43% increase in carrier mobility, while the intragrain carrier scattering time (≈110 fs) remains unchanged. These results demonstrate that the enhanced photoconductivity originates from reduced carrier backscattering at grain boundaries, rather than changes in intragrain carrier scattering. Our results provide microscopic insight into the mechanism underlying the improved performance of solar cells based on mixed-cation, mixed-halide hybrid perovskites passivated with CsPbBr3 quantum dots.