High-performance ReS₂ photodetectors with graphene auxiliary layers and NbSe₂ electrodes

Photodetectors (PDs) are vital in optical communications, environmental monitoring, and military applications. At present, conventional PDs face challenges such as high dark current, which restricts their further development in high-performance photodetection. Two-dimensional (2D) materials offer advantages for next-generation photodetection due to their atomic thickness, defect-free surfaces, and gate-tunable bandgaps, which enable efficient channel modulation and ultralow dark current. This work presents a high-performance phototransistor that integrates topological semimetal NbSe₂ source/drain electrodes and an underlying graphene (Gr) auxiliary layer to construct a ReS₂/Gr heterojunction. The NbSe₂ contacts mitigate Fermi-level pinning, while the underlying Gr auxiliary layer, not directly contacted by electrodes, significantly enhances device performance. At 14.9 mW/cm² of light intensity and −20 V of gate voltage, the ReS₂/Gr device shows a higher responsivity of 1261.59 mA/W, which is 1726% higher than that of the ReS₂ device. Besides, the specific detectivity and external quantum efficiency (D^* = 7.20 × 10¹¹ Jones and EQE = 2.29 × 10⁴%) are much larger than those of the ReS₂ device (D^* = 4.17 × 10¹⁰ Jones and EQE = 171%). The ReS₂/Gr device also exhibits faster response speeds (t_rise = 32.5 μs, t_fall = 45.7 μs) compared to the ReS₂ device (t_rise = 3.23 ms, t_fall = 4.27 ms), demonstrating a two-order-of-magnitude improvement in temporal response. Moreover, it shows excellent performance in optical communications and single-pixel imaging, successfully decoding an ASCII signal and capturing a high-contrast pattern. These results validate its potential for practical applications in optical communication and imaging, offering a representative demonstration for the optimization of 2D material PDs.