Visualizing carrier dynamics of a semiconductor film photodetector optimized by interface passivation

To enhance photodetector performance, transient absorption (TA) microscopy is employed for the first time, to the best of our knowledge, to investigate carrier diffusion in interface-passivated semiconductor polycrystalline films. TA analysis reveals that after passivation with DMMI-Cl, the carrier diffusion length in MASnBr₃ polycrystalline films increases from 109 nm to 123 nm, while the diffusion coefficient improves from 0.119 cm² s^-1 to 0.151 cm² s^-1. Furthermore, DMMI-Cl passivation suppresses carrier losses from monomolecular and Auger recombination and promotes bimolecular recombination. The resulting photodetector exhibits a nearly six-fold enhancement in responsivity (R = 4.09 AW^-1), giving it a strong standing among reported 3D hybrid Sn-based perovskite photodetectors. This work expands the application scope of TA microscopy, provides deeper insight into grain-boundary-modulated spatiotemporal carrier dynamics, and contributes significantly to the development of high-performance tin-based photodetectors.