Piezotronic effect on interfacial charge modulation in mixed-dimensional Van der Waals heterostructure for ultrasensitive flexible photodetectors

Van der Waals (vdWs) heterostructure is emerging as one of the most interesting systems in next-generation flexible optoelectronics. Furthermore, the gate-tunability of vdWs heterostructure is widely applied to enhance the performance of various devices, which is generally achieved by external electric field. However, in-plane cracking and slippage of gate electrode restricted this external electric field modulation in flexible devices. Here, we propose a distinctive strain-gating method to manipulate 2D WSe2-1D ZnO vdWs interfacial charge and modulate its photosensing performance by tuning electronic states of WSe2. With increasing tensile strain, the device shows obvious enhancing photocurrent and the corresponding photoresponsivity reaches up to 394 mA W-1 under white light illumination. Such performance enhancement can be attributed to strain-induced piezopolarization charges on ZnO nanobelt polar surface, which function as gate to tune the local transport of photogenerated carriers at the WSe2-ZnO vdWs interface. This work provides a new strategy to achieve interaction between vdWs interface and strain stimuli, which broadens applications of functional vdWs heterostructure for next-generation photodetection or imaging.