Dual-Polarity Switching in Self-Powered Ag/MoS2/Ag Photodetectors

Here, we report the photoresponse of a Ag-MoS2–Ag-based metal–semiconductor–metal (MSM) device emphasizing the importance of the silver electrode. The device displayed self-powered photoresponse to a wide band of incident light (from UV to NIR range) along with photocurrent switching at two different wavelengths, 610 nm (visible region) and 1050 nm (NIR region). Maximum photocurrent of 8.41 nA and responsivity of 0.9 mA W–1 were obtained at 900 nm. The uneven distribution of silver nanoprisms in the electrodes is expected to induce asymmetry in local surface plasmon resonance (LSPR) under broad band light illumination, producing a lead-lag in the carrier injection into the semiconducting layer. The nanolevel asymmetry in silver electrodes along with the photoresponse characteristics of a few layers of the MoS2 system is identified as the plausible reason for the self-powered and dual-polarity photoresponse displayed by the device. The energy band diagram is analyzed to substantiate the device behavior.