Self-driven photo-polarized water molecule triggered graphene-based photodetector

TL;DR

This paper demonstrates a novel graphene-based photodetector activated by polarized water, capable of high sensitivity and tunable wavelength detection, with potential applications in health monitoring and electronic devices.

Contribution

It introduces a water-triggered photodetector using polarized water sandwiched between graphene and semiconductor, enabling high performance without lattice matching constraints.

Findings

Achieves responsivity of 130.7 mA/W at 350 nm

Detects blood oxygen saturation with ~1.9% error

Operates effectively under zero bias voltage

Abstract

Flowing water can be used as an energy source for generators, providing a major part of the energy for daily life. However, water is rarely used for information or electronic devices. Herein, we present the feasibility of a polarized liquid-triggered photodetector in which polarized water is sandwiched between graphene and semiconductor. Due to the polarization and depolarization processes of water molecular under the driven of photogenerated carriers, a photo-sensitive current can be repeatably produced, resulting in a high-performance photodetector. The response wavelength of the photodetector can be finely tuned as a result of the free choice of semiconductors as there is no requirement of lattice match between graphene and the semiconductors. Under zero voltage bias, the responsivity and specific detectivity of Gr/NaCl (0.5 M)/N-GaN reaches values of 130.7 mA/W and 2.8*10^12 Jones under 350 nm illumination. Meanwhile, using a polar liquid photodetector can successfully read the photoplethysmography signals to produce accurate oxygen blood saturation and heart rate. Compared with the commercial pulse oximetry sensor, the average errors of oxygen saturation and heart rate in the designed photoplethysmography sensor are~1.9% and ~2.1%, respectively. This study transfers the message that water can be used as high-performance photodetector in informative industries.