High-quality two-dimensional atomic layered p–n heterostructures are essential for high-performance integrated optoelectronics. The studies to date have been largely limited to exfoliated and restacked flakes, and the controlled growth of such heterostructures remains a significant challenge. Here we report the direct van der Waals epitaxial growth of large-scale WSe2/SnS2 vertical bilayer p–n junctions on SiO2/Si substrates, with the lateral sizes reaching up to millimeter scale. Multi-electrode field-effect transistors have been integrated on a single heterostructure bilayer. Electrical transport measurements indicate that the field-effect transistors of the junction show an ultra-low off-state leakage current of 10−14 A and a highest on–off ratio of up to 107. Optoelectronic characterizations show prominent photoresponse, with a fast response time of 500 μs, faster than all the directly grown vertical 2D heterostructures. The direct growth of high-quality van der Waals junctions marks an important step toward high-performance integrated optoelectronic devices and systems.

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2D vertical van der Waals (vdW) heterostructures with atomically sharp interfaces have attracted tremendous interest in 2D photonic and optoelectronic applications. Band alignment engineering in 2D heterostructures provides a perfect platform for tailoring interfacial charge transfer behaviors, from which desired optical and optoelectronic features can be realized. Here, by developing a two‐step chemical vapor deposition strategy, direct vapor growth of monolayer PbI 2 on monolayer transition metal dichalcogenides (TMDCs) (WS 2 , WSe 2 , or alloying WS 2(1− x ) Se 2 x ), forming bilayer vertical heterostructures, is demonstrated. Based on the calculated electron band structures, the interfacial band alignments of the obtained heterostructures can be gradually tuned from type‐I (PbI 2 /WS 2 ) to type‐II (PbI 2 /WSe 2 ). Steady‐state photoluminescence (PL) and time‐resolved PL measurements reveal that the PL emissions from the bottom TMDC layers can be modulated from apparently enhanced (for WS 2 ) to greatly quenched (for WSe 2 ) compared to their monolayer counterparts, which can be attributed to the band alignment–induced distinct interfacial charge transfer behaviors. The band alignment nature of the heterostructures is further demonstrated by the PL excitation spectroscopy and interlayer exciton investigation. The realization of 2D vertical heterostructures with tunable band alignments will provide a new material platform for designing and constructing multifunctional optoelectronic devices.

Two-dimensional (2D) atomic layered semiconductor (e.g., transition metal dichalcogenides, TMDCs) heterostructures display diverse novel interfacial carrier properties and have potential applications in constructing next generation highly compact electronics and optoelectronics devices. However, the optoelectronic performance of this kind of semiconductor heterostructures has difficulty reaching the expectations of practical applications, due to the intrinsic weak optical absorption of the atomic-thick component layers. Here, combining the extraordinary optoelectronic properties of quantum-confined organic–inorganic hybrid perovskite (PVK), we design an ultrathin PVK/TMDC vertical semiconductor heterostructure configuration and realize the controlled vapor-phase growth of highly crystalline few-nanometer-thick PVK layers on TMDCs monolayers. The achieved ultrathin PVKs show strong thickness-induced quantum confinement effect, and simultaneously form band alignment-engineered heterointerfaces with the underlying TMDCs, resulting in highly efficient interfacial charge separation and transport. Electrical devices constructed with the as-grown ultrathin PVK/WS2 heterostructures show ambipolar transport originating from p-type PVK and n-type WS2, and exhibit outstanding optoelectronic characteristics, with the optimized response time and photoresponsivity reaching 64 μs and 11174.2 A/W, respectively, both of which are 4 orders of magnitude better than the heterostructures with a thick PVK layer, and also represent the best among all previously reported 2D layered semiconductor heterostructures. This work provides opportunities for 2D vertical semiconductor heterostructures via incorporating ultrathin PVK layers in high-performance integrated optoelectronics.