Transient Spectroscopic Imaging Promotes Interface-Passivated Photodetector for High Performance

Optimizing semiconductor charge-carrier dynamics is pivotal for boosting device performance, yet the lack of spatiotemporal-resolved characterization methods forces iterative device fabrication to realize such optimization. Here, we develop transient spectroscopic imaging (TSI) techniques, combining local transient photoluminescence and transient absorption microscopy, to directly visualize intra- and intergrain carrier dynamics and guide the micronano-scale interface optimization of devices. Using TSI, we study 4-fluorobenzoyl amide (FBA)-passivated two-dimensional (2D) BA₂PbI₄ perovskite films, revealing that FBA passivation suppresses intragrain and intergrain carrier recombination behavior and elevates the intragrain diffusion coefficient (D) from 1.1 × 10⁴ to 1.9 × 10⁴ nm² ns^-1 and the diffusion length from 181.7 to 477.5 nm, respectively. Correspondingly, FBA-passivated photodetectors (PDs) exhibit exceptional performance, achieving a responsivity of 39.0 A W^-1 under 9.9 nW cm^-2 illumination (meeting weak-light detection criteria ≤ 0.1 μW cm^-2) and a linear dynamic range of 139.2 dB, ranking among the best 2D Ruddlesden-Popper perovskite PDs. For the first time, integrating this PD into a single-pixel imaging system enables high-fidelity image reconstruction and recognition via correlation and compressive sensing algorithms. This work establishes a robust platform for carrier dynamics analysis, deepens the mechanistic understanding of PD operation, and expands the application of 2D perovskite devices in image recognition.