In-Plane Strain-Modulated Photoresponsivity of the α-In₂Se₃-Based Flexible Transistor

Two-dimensional (2D) van der Waals (vdW) materials have been proven to be functional materials with excellent performance among flexible functional optoelectronics. Static strain may have a great influence on photoinduced charge carriers in a 2D vdW piezoelectric semiconductor. However, only a few works pay attention to the static-strain-modulated photoresponsivity of 2D vdW ferroelectric materials. α-In2Se3, a 2D vdW ferroelectric semiconductor from the family of III–VI compounds in the form of III2–VI3, has attracted considerable attention for the study of high-performance nanodevices. In this study, we investigate a flexible α-In2Se3-based transistor on a polyethylene terephthalate substrate. A competitive mechanism of carrier mobility and piezoelectric/ferroelectric polarization exists in the transistor when in-plane strain is applied. The carrier mobility modulates separation and transport of electron–hole pairs, whereas piezoelectric/ferroelectric polarization charges modulate the local band profile tilting. The optimized photoresponsivity is increased by 200% (illumination intensity is about 454 μW/cm2) while introducing a −0.15% compressive strain when the wavelength of the laser is about 405 nm. Our results reveal the strain-modulated photoresponsivity in an α-In2Se3-based flexible transistor, which may offer an approach to understand strain-modulated flexible functional optoelectronics.