High-Responsivity\nMultiband and Polarization-Sensitive\nPhotodetector Based on the TiS₃/MoS₂ Heterojunction

Abstract

Two-dimensional (2D) material photodetectors\nhave received\nconsiderable\nattention in optoelectronics as a result of their extraordinary properties,\nsuch as passivated surfaces, strong light–matter interactions,\nand broad spectral responses. However, single 2D material photodetectors\nstill suffer from low responsivity, large dark current, and long response\ntime as a result of their atomic-level thickness, large binding energy,\nand susceptibility to defects. Here, a transition metal trichalcogenide\nTiS₃ with excellent photoelectric characteristics, including\na direct bandgap (1.1 eV), high mobility, high air stability, and\nanisotropy, is selected to construct a type-II heterojunction with\nfew-layer MoS₂, aiming to improve the performance of 2D\nphotodetectors. An ultrahigh photoresponsivity of the TiS₃/MoS₂ heterojunction of 48 666 A/W at 365 nm, 20 000\nA/W at 625 nm, and 251 A/W at 850 nm is achieved under light-emitting\ndiode illumination. The response time and dark current are 2 and 3\norders of magnitude lower than those of the current TiS₃ photodetector with the highest photoresponsivity (2500 A/W), respectively.\nFurthermore, polarized four-wave mixing spectroscopy and polarized\nphotocurrent measurements verify its polarization-sensitive characteristics.\nThis work confirms the excellent potential of TiS₃/MoS₂ heterojunctions for air-stable, high-performance, polarization-sensitive,\nand multiband photodetectors, and the excellent type-II TiS₃/MoS₂ heterojunction system may accelerate the design\nand fabrication of other 2D functional devices.