Observation of ambipolar photoresponse from 2D MoS₂/MXene heterostructure

Two-dimensional materials have been demonstrated as promising toolboxes for optoelectronics. Transition metal carbides and nitrides (MXenes), members of an emerging family of two-dimensional materials, have drawn extensive attention in optoelectronics owing to their excellent conductivity and tunable electronic properties. Herein, a photodetector based on the two-dimensional van der Waals heterostructure of Ti₃C₂T_x MXene and a MoS₂ monolayer was constructed to observe the ambipolar photoresponse, which showed a positive photoresponse in the visible spectrum (500–700 nm) and a negative photoresponse at longer wavelengths (700–800 nm). The device exhibited a high negative responsivity of 1.9 A/W and a detectivity of 2.1 × 10¹⁰ Jones under 750 nm light illumination. Detailed experiments demonstrate that the negative photoresponse arises from the heterostructure- induced trap energy level, which confines the excited photoelectrons and leads to an inverse current. This work demonstrates a unique optoelectronic phenomenon in MoS₂/MXene heterostructures and provides valuable insights into the development of new photodetection materials.