Strain engineering for enhanced photoresponse of multilayer InSe flexible devices with a metal-semiconductor-metal...

Strain engineering has been a promising strategy for enhancing the properties of electronics and optoelectronics based on two-dimensional (2D) materials, which exhibit extraordinary mechanical, electrical and optical properties. However, two-terminal flexible photodetectors of 2D InSe with metal-semiconductor-metal (MSM) structures, which have emerged as one of the most compelling devices due to their superior electron mobility and broadly tunable bandgap, lack systematic research on their strain-dependent electrical and photoelectrical properties. Here, we experimentally demonstrate a strain-enhanced photoresponse behavior in multilayer InSe devices with both symmetric Au/InSe/Au contacts and asymmetric Gr (graphene)/InSe/Au junctions by applying controlled tensile strain. The photocurrent of the Au/InSe/Au device increases by more than one order of magnitude (>10×) under 0.8% tensile strain at three excitation wavelengths (532, 633, and 785 nm), accompanied by a reduction in the device response time. A similar strain-enhanced photocurrent was also observed in the asymmetric Gr/InSe/Au devices. The devices returned to their initial state upon strain release after 100 cycles, demonstrating excellent mechanical robustness. These results highlight the efficacy of strain engineering in multilayer InSe devices for enhancing their photoresponse, offering a promising route toward high-performance flexible optoelectronics.