Unlocking the Performance Trade-off in Metal Phosphorus Trichalcogenides-Based Optoelectronics.

Two-dimensional van der Waals heterojunctions present a promising platform for advanced optoelectronic devices. Yet, achieving self-powered operation with overall performance metrics remains challenging, especially for devices based on emerging metal phosphorus trichalcogenides (MPTs), which have historically underperformed. To tackle this issue, we constructed an optimal type-I heterojunction by integrating FePSe3 with WSe2, both featuring Se-terminated surfaces. The resulting built-in potential, confirmed to be 0.18 eV through Kelvin probe force microscope and ultraviolet photoelectron spectroscopy measurements, facilitates efficient, self-driven carrier separation. Our photodetector demonstrates an impressive combination of properties at zero bias: a high responsivity of ∼59.1 mA/W, an ultralow dark current at the 0.4 pA level, an exceptional specific detectivity of 1.2 × 1011 Jones, and a rapid response time of 49.8 μs. It shows broadband sensitivity from ultraviolet (250 nm) to near-infrared (950 nm) with distinct spectral discriminability, supported by a high photocurrent on/off ratio of 5.8 × 104. The practical viability is further validated through high-speed, single-pixel imaging application and low-noise optical communication without any power consumption. This work not only sets a performance benchmark for MPT-based photodetectors but also establishes a versatile material platform for next-generation, low-power imaging and intelligent spectrally selective sensing technologies.