Strain Improving the Performance of a Flexible Monolayer MoS2 Photodetector

The mechanically stretchable 2D materials have attracted much interest for their potential applications in flexible electronics, as well as the possibility of strain-tuning their electronic and photoelectric performance through piezoelectric and piezoresistive effects. Piezoelectric and piezoresistive effects are observed in a flexible monolayer MoS2 device and the effect of the strain on the photoelectric properties is investigated. The light-dark current ratio, photoresponse speed, and self-powered current are significantly improved by piezoelectric effect when 0.8% strain is applied in the armchair direction of monolayer MoS2. In addition, the photocurrent and photoresponsivity are increased by 5.6 and 4.2, respectively, due to large piezoresistive effect when 1.4% strain is applied in a zigzag direction. Furthermore, the piezoelectric and piezoresistive effects in monolayer MoS2 are characterized by Kelvin probe force microscopy (KPFM). The regulation mechanism of piezoelectric and piezoresistive effect on the photoelectric performance of the MoS2 photodetector is discussed using the energy band. The results show that the photoelectric performance of 2D materials can not only be improved by the piezoelectric effect, but also by the piezoresistive effect, which is significant for the application of 2D materials in optoelectronics.