With the rapid development of materials applications, the limitation of a single layer material has become more apparent and its intrinsic properties can no longer satisfy the growing demand. The construction of van der Waals (vdW) heterostructures is an effective way to address this issue. Here, the heterostructure stability, excitation transfer mechanism, carrier mobility and multiple energy conversion performance of MoTe2/As stacking have been studied using first-principles calculations. Binding energy and AIMD simulation analyses show that the ductile, type-II indirect band gap MoTe2/As heterostructure acquires satisfactory thermal stability along with a small lattice mismatch of 1.5%, a high carrier mobility (up to 736.06 cm(2) V-1 s(-1)), a high solar absorbance on the 10(5) cm(-1) order across the infrared-ultraviolet region, a spectroscopic limited maximum efficiency (SLME) exceeding 30% and a large built-in electric field at the interface, rendering this heterostructure suitable for nanoscale optoelectronics applications. Under optimal hole doping, the calculated electronic transport parameters reveal a combined moderate figure of merit (ZT > 0.6) and an impressive power factor (PF > 48.0 mW m(-1) K-2) at a temperature of above 700 K. More remarkably, the heterostructure has band edge positions straddling the water redox potential for pH scale of 0-4 under a 4% biaxial compressive strain, which leads to commercially compliant solar-to-hydrogen (STH) energy conversion efficiencies of 30%. These results provide a clear underlying description of the potential of a MoTe2/As heterojunction as a multifunctional energy material.