This study investigates the electronic and optoelectronic properties of van der Waals (vdW) heterostructures composed of single-layer transition metal dichalcogenides (TMDCs) such as WSe2 and MoS2. The authors fabricate and characterize these heterostructures, which are built by stacking individual single-layers of WSe2 and MoS2. They observe a significant Stokes-like shift of ~100 meV between the photoluminescence peak and the lowest absorption peak, indicating spatially indirect emission and strong interlayer coupling of charge carriers. This coupling can be tuned by inserting dielectric layers, such as hexagonal boron nitride (h-BN), into the vdW gap. The results suggest that this interlayer coupling provides a new degree of freedom in band engineering, potentially leading to a new family of semiconductor heterostructures with tunable optoelectronic properties. The study also explores carrier transport across the hetero-interface, demonstrating rectifying behavior consistent with type II band alignment. Overall, the findings highlight the potential of TMDC-based heterostructures for advanced electronic and optoelectronic applications.This study investigates the electronic and optoelectronic properties of van der Waals (vdW) heterostructures composed of single-layer transition metal dichalcogenides (TMDCs) such as WSe2 and MoS2. The authors fabricate and characterize these heterostructures, which are built by stacking individual single-layers of WSe2 and MoS2. They observe a significant Stokes-like shift of ~100 meV between the photoluminescence peak and the lowest absorption peak, indicating spatially indirect emission and strong interlayer coupling of charge carriers. This coupling can be tuned by inserting dielectric layers, such as hexagonal boron nitride (h-BN), into the vdW gap. The results suggest that this interlayer coupling provides a new degree of freedom in band engineering, potentially leading to a new family of semiconductor heterostructures with tunable optoelectronic properties. The study also explores carrier transport across the hetero-interface, demonstrating rectifying behavior consistent with type II band alignment. Overall, the findings highlight the potential of TMDC-based heterostructures for advanced electronic and optoelectronic applications.