Broadband photodetection, spanning from ultraviolet (UV) to infrared (IR), is pivotal in diverse technological domains including astronomy, remote sensing, environmental monitoring, and medical diagnostics. However, current commercially available broadband photodetectors, predominately based on conventional narrow-bandgap semiconductors, exhibit limited sensitivity in the UV region. This limitation, stemming from the significant energy disparity between the semiconductor bandgap and UV photon, narrows their application scope. Herein, we report an innovative approach involving the in-situ van der Waals (vdW) integration of two-dimensional (2D) GeSe₂ layers onto a Si substrate. This process yields a high-quality GeSe₂/Si vdW heterojunction device, which features a broad response range covering from UV to near-IR (NIR) with a greatly-enhanced sensitivity in the UV region. The device possesses high responsivities of 325 and 533.4 mA/W, large detectivities of 1.24 × 10¹³ and 2.57 × 10¹³ Jones, and fast response speeds of 20.6/82.1 and 17.7/81.0 μs under 360 and 980 nm, respectively. Notably, the broadband image sensing and secure invisible optical communication capabilities of the GeSe₂/Si heterojunction device are demonstrated. Our work provides a viable approach for UV-enhanced broadband photodetection technology, opening up new possibilities and applications across various scientific and technological domains.