Efficient Dark Current Suppression by Engineering PIET‐Active Discrete Donor–Acceptor Architecture for High‐Sensitivity Semiconductor Photodetectors

High-sensitivity photodetectors are of paramount importance for astronomy, night vision, and bioimaging. Current methods for enhancing sensitivity still face the challenges of complex preparation processes and the dependence on low-temperature environments. This work demonstrates that constructing a discrete, donor (D)-acceptor (A) structure and employing the photoinduced electron transfer (PIET) technique may simultaneously reduce dark current and increase photocurrent efficiently, thereby significantly enhancing the detection sensitivity. With this synergetic strategy, a viologen-based photochromic semiconductor with a discrete bismuth halide structure may reduce its dark current by ≈94% -a reduction far exceeding those reported using external field-induced modification methods-while simultaneously enhancing the photocurrent by ≈83% after PIET and coloration. This value corresponds to a two-fold increase of the detection sensitivity (S). This finding opens a new effective strategy to explore ultra-highsensitivity photodetectors and smart semiconductors.