Covalent Aminopropyl Functionalization Tailors Ti₃C₂T_x MXene for High-Performance Flexible NIR Photodetectors

Ti₃C₂T_x MXene, with its exceptional electrical conductivity, mechanical flexibility, and processability, compatible with wearable and integrated systems, plays a crucial role in advancing flexible photodetectors for intelligent perception systems and bioinspired artificial vision. However, its intrinsic narrow bandgap (< 0.1 eV) and the limited diversity of surface functionalization strategies severely constrain its use as a photosensitive layer in photodetectors. Herein, a surface engineering strategy is developed to covalently graft aminopropyl groups onto the surface of Ti₃C₂T_x via Si-O-Ti linkages, thereby successfully widening its bandgap to 1.46 eV. The resulting Au/Ti₃C₂T_x-NH₂/Au flexible photodetector exhibits excellent bending resistance and demonstrates an ultrahigh on–off ratio of 10¹² under 808 nm laser excitation, along with an excellent responsivity of 3.72 × 10⁴ A W⁻¹ and high specific detectivity of 1.03 × 10¹⁸ Jones. Additionally, the fabricated 147-pixel image sensor achieves high-contrast imaging of the “MAX” pattern, providing a new pathway for advancing high-performance flexible near-infrared photodetector technologies in bioinspired vision and flexible wearable image sensing.