Van der Waals (vdW) heterojunctions, with their unique electronic and optoelectronic properties, have become promising candidates for photodetector applications. Amplifying the contribution of the depletion region in vdW heterojunction, which would enhance both of the collection efficiency and speed of the photogenerated carriers, presents an effective strategy for achieving high performance vdW heterojunction photodetectors. Herein, a fully depleted vdW heterojunction photodetector is built on two-dimensional (2D) semiconductor materials (GaTe and InSe) layered on a pattered bottom electrode in vertical structure, in which the generation and motion of carriers are exclusively achieved in the depletion region. Attributed to the intrinsic built-in electric field, the elimination of series resistance and the depletion region confinement of carriers, the as-fabricated photodetector exhibits prominent photovoltaic properties with a high open-circuit voltage of 0.465 V, as well as photoresponse characteristics with outstanding responsivity, detectivity and photoresponse speed of 63.7 A/W, 3.88 × 10¹³ Jones, and 32.7 μs respectively. The overall performance of this fully depleted GaTe/InSe vdW heterojunctions photodetectors are ranking high among the top level of 2D materials based photodetectors. It indicates the device architecture can provide new opportunities for the fabrication of high-performance photodetectors.

Although photodetection based on two-dimensional (2D) van der Waals (vdWs) P–N heterojunction has attracted extensive attention recently, their low responsivity (R) due to the lack of carrier gain mechanism in reverse bias or zero bias operation hinders their applications in advanced photodetection area. Here, a black phosphorus/rhodamine 6G/molybdenum disulfide (BP/R6G/MoS₂) photodiode with high responsivity at reverse bias or zero bias has been achieved by using interfacial charge transfer of R6G molecules assembled between heterojunction layers. The formed vdWs interface achieves high performance photoresponse by efficiently separating the additional photogenerated electrons and holes generated by R6G molecules. The devices sensitized by the dye molecule R6G exhibit enhanced photodetection performance without sacrificing the photoresponse speed. Among them, the R increased by 14.8–20.4 times, and the specific detectivity (D*) increased by 24.9–34.4 times. The strategy based on interlayer assembly of dye molecules proposed here may pave a new way for realizing high-performance photodetection based on 2D vdWs heterojunctions with high responsivity and fast response speed.