Two-dimensional (2D) van der Waals heterostructures based on various 2D transition metal dichalcogenides are widely used in photodetection applications. However, their response time and photoresponsivity are limited, posing a challenge for their applications in high-sensitivity photodetection. Surface charge transfer doping (SCTD) has emerged as a novel doping approach for low-dimensional materials with high specific surface area and attracted considerable attention, as it is simple and effective, does not damage the lattice, and considers various types of dopants. Herein, we prepare p-i-n junction-based photodetectors via the SCTD of WSe₂/ReS₂ heterojunctions using p-type dopant F₄-TCNQ molecules, where doped WSe₂ serves as a p-type semiconductor, undoped WSe₂ acts as an intrinsic layer, and ReS₂ functions as an n-type semiconductor. The surface-charge-transfer-doped WSe₂/ReS₂ heterojunction leads to a reduction in the Schottky barrier and an increase in the built-in electric field compared with the as-fabricated heterojunction. In the photovoltaic mode and under 785 nm laser illumination, the photodiode exhibits an increase in responsivity from 0.08 to 0.29 A/W, specific detectivity from 1.89 × 10¹² to 8.02 × 10¹² Jones, and the external quantum efficiency from 12.67 to 46.29%. Additionally, the p-i-n structure expands the depletion region width, resulting in a photovoltaic response time of 7.56/6.48 μs and a -3 dB cutoff frequency of over 85 kHz, an order of magnitude faster than the pristine response time. Herein, we derive an effective and simple scheme for designing high-performance, low-power optoelectronic devices based on 2D van der Waals heterostructures.

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