The stacking of two-dimensional (2D) materials is a highly effective approach in the design of high-performance optoelectronic devices. In this study, we propose a novel Janus monolayer-based 2D/2D van der Waals heterostructure (vdWH) called SbTeBr/SbSI. Starting from its most stable binding configuration, we systematically examined its electronic, optical, mechanical and dynamical properties. The SbTeBr/SbSI vdWH exhibits a type II band arrangement, with an indirect bandgap of 1.28 eV and strong light absorption capabilities in the visible range, achieving an absorption coefficient of 4 × 105 cm-1. These desirable properties suggest that SbTeBr/SbSI holds promise as a material for solar cells, potentially achieving a power conversion efficiency of 8.3%. The dipole-induced electric field in the SbTeBr/SbSI vdWH leads to significant differences in the mobilities of different carriers, which is a critical aspect in suppressing the recombination of photogenerated carriers. Additionally, according to the simulations of nonadiabatic molecular dynamics, a long electron-hole recombination time of 133 ps is predicted. Thus, the SbTeBr/SbSI heterostructure enables efficient charge separation, demonstrating its potential as a high-performance optoelectronic material.