An Organic Electrochemical Transistor Integrated Photodetector for High Quality Photoplethysmogram Signal Acquisition

摘要

The organic photodiode (OPD) is a promising building block for solutionprocessable,flexible, lightweight, and miniaturized photodetectors, ideal forwearable applications. Despite the advances in materials used in OPDs, theirphotocurrent and light responsivity are limited, and alternative methods arerequired to boost the signal response. Herein, a miniaturized organic electrochemicaltransistor (OECT) is integrated with an OPD module to unlock thepotential of OPDs to acquire physiological signals. In this integrated photodetector(IPD) system, the light intensity regulates the OPD voltage outputthat modulates the OECT channel current. The high transconductance of theOECT provides efficient voltage-to-current conversion, enhancing the signalto-noise ratio on the sensing site. A microscale, p-type enhancement-modeOECT with high gm and fast switching speed performs better in this applicationthan depletion-mode OECT of the same geometry. The IPD achievesa photocurrent and responsivity 318 and 140 times higher than the standaloneOPD, respectively. It is shown that with the IPD, the amplitude of thephotoplethysmogram signals detected by the OPD is enhanced by a factorof 2.9 × 10~3, highlighting its potential as a wearable biosensor and to detectweak, often uncaptured, light-based signals from living systems.