High-Performance Planar Ni/Si Photothermoelectric Photodetectors Enabled by MnO2 Nanosheets

Photodetectors are the key component of modern communication systems, surveillance applications, robotics, and scientific research. The photothermoelectric effect offers opportunity to fabricate broadband and self-driven photodetectors utilizing thermally energized charge carriers. Unfortunately, photothermoelectric photodetectors are facing the challenge of large dark current, leading to low detectivity, linear dynamic range, and on-off ratio. Herein, we design a planar Ni/n-Si device structure with the help of a monolayer of MnO2 nanosheets for contact engineering. The demonstrated device shows a broadband detection range from 200 nm to MIR with an external quantum efficiency of 263.6%, a photoresponsivity of 455.1 mA W-1, a detectivity of ∼7.25 × 1012 Jones, and an on-off ratio of ∼103 at 0 V. Additionally, the device shows an unprecedented bias-assisted photoresponsivity and external quantum efficiency of 21.56 A W-1 and 13,363%, respectively, with 200 nm illumination at -10 V. The nanosheet-based contact engineering provides a powerful strategy to fabricate self-powered photodetectors with high photoresponsivity, external quantum efficiency, and broadband detection from the solar blind region to the MIR spectrum.