CsPbBr 3 Quantum Dot Sensitization Enabled Type‐III SnSe 2 /MoTe 2 Heterojunction for Fast and Self‐Powered Visible Photodetection

ABSTRACT Self‐powered photodetectors based on type‐III two‐dimensional (2D) heterojunctions are attractive for zero‐bias operation, yet their visible light responsivity is often limited by insufficient photocarrier generation in atomically thin absorbers. Here, we report a sensitized self‐powered visible photodetector in which CsPbBr 3 quantum dots (QDs) are integrated with a type‐III SnSe 2 /MoTe 2 heterojunction. Due to the built‐in potential difference of 0.24 V between the CsPbBr 3 QDs and SnSe 2 , the resulting built‐in electric field enables directional hole injection from CsPbBr 3 into SnSe 2 . This increases the number of photogenerated carriers participating in photovoltaic conversion and suppresses recombination. Under 405 nm illumination at zero bias, the optimized device delivers a responsivity (R) of 764.4 mA W −1 , an external quantum efficiency (EQE) of 245.2%, a specific detectivity (D * ) of 2 × 10 12 Jones, and a microsecond‐scale response time of 740/960 µs. The device also exhibits stable cycling behavior and practical capability in imaging and optical logic applications. This work provides a viable strategy for enhancing self‐powered visible photodetection by coupling a strongly absorbing QD sensitizer with a type‐III 2D heterojunction.