in TMDC families, possesses a direct band gap of 1.55 eV, high photoluminescence, and large exciton binding energy. [5,6] Compared to other TMDCs, it exhibits higher optical absorption (5-10%), which is beneficial for sensitive photodetection. [7] However, similar to other TMDCs, MoSe 2 also suffered from the impurities, scattering, and structural defects, significantly limited the device performance. [8,9] It is known that high photosensitivity and fast response speed are critical for practical photodetectors in modern industrial and scientific applications. [10][11][12][13] For instance, the commercial silicon detector possess a specific detectivity of over 10 12 Jones and a response speed of less than 100 µs. [2] For MoSe 2 -based photodetectors, it is challenging to achieve such high performance due to the difficulty in controllable doping. [14] To date, various approaches have been reported to improve the device performance, especially employing homojunction or heterojunction to introduce a strong builtin electric field. Jie et al. reported a MoSe 2 /Si heterojunction photo detector, which achieved an ultrafast response speed of ≈270 ns due to the high in-plane mobility that ensured the fast separation and transport of photogenerated carriers. [14] However, its low detectivity (7.13 × 10 10 Jones) still cannot meet the requirements for practical applications. Chen et al. prepared a molybdenum disulfide/molybdenum diselenide (MoS 2 /MoSe 2 ) lateral heterojunction by chemical vapor deposition, which demonstrated a matched band alignment of MoS 2 and MoSe 2 , and strong donor-acceptor delocalization effect, resulting in an optimal responsivity of 1.3 A W −1 and detectivity of 2.6 × 10 11 Jones. [15] Unfortunately, the inherent defects in MoS 2 leads a slow response time of 0.6 s. Zhen et al. reported a high-performance MoSe 2 homojunction infrared photodetector, exhibiting a high responsivity and fast response speed, but low detection rate. [16] Although these reported works demonstrated improved device performance, the fabrication procedures are complicated and difficult to control. Meanwhile, these strategies mainly focused on improving a single parameter, but part of figuresof-merits was scarified. Apart from the structural engineering, the device performance is limited by the intrinsic defects within MoSe 2 and impurities at the interface. [17,18] Specifically, the oxygen (O 2 ) and water (H 2 O) molecules from ambient atmosphere are easily adhered on the surface of MoSe 2 films, due to the presence of numerous intrinsic vacancies. This not only