Gate-tunable WSe2/Bi2Te2Se van der Waals heterostructure photodetectors for broadband photodetection

Band offset engineering of van der Waals heterostructures is a critical strategy to broaden the response range of optoelectronic devices and realize multifunctional device applications, and the adoption of high-mobility material systems in heterostructure design is essential for optimizing the overall performance of optoelectronic devices. Herein, we design and fabricate a Type-II band alignment van der Waals heterostructure based on n-type Bi2Te2Se and p-type WSe2, with strong interlayer coupling at the heterointerface verified via systematic structural and spectroscopic characterizations. The devices exhibit a prominent photovoltaic effect with clear open-circuit voltage and short-circuit current, enabling stable self-powered photodetection at zero bias without any external power supply. This self-powered photodetection exhibits excellent performance over an ultra-broadband from 254 to 1310 nm, delivering a maximum responsivity of 0.22 A/W and a high specific detectivity of 4.3 × 109 Jones. More importantly, they present a distinct gate-tunable transition from p-type dominated ambipolar transport to n-type dominated unipolar transport, with the responsivity magnified by 3 times via rational gate voltage regulation. Spatially resolved photocurrent mapping directly visualizes the gate-enhanced photocarrier separation at the heterointerface, and the device further enables high-quality broadband photoelectric imaging and convolutional neural network-based image recognition. This work establishes a reliable platform for ternary Bi-based heterostructures, highlighting their potential for low-power, multifunctional optoelectronics and next-generation artificial vision systems.