  Strain engineering, which aims to tune the bandgap of a semiconductor by the
application of strain, has emerged as an interesting way to control the
electrical and optical properties of two-dimensional (2D) materials. Apart from
the changes in the intrinsic properties of 2D materials, the application of
strain can be also used to modify the characteristics of devices based on them.
In this work, we study flexible and transparent photodetectors based on
single-layer MoS2 under the application of biaxial strain. We find that by
controlling the level of strain, we can tune the photoresponsivity (by 2-3
orders of magnitude), the response time (from <80 ms to 1.5 s) and the spectral
bandwidth (with a gauge factor of 135 meV/% or 58 nm/%) of the device.
