Non-Fullerene Acceptor Organic Photodetector for Skin-Conformable Photoplethysmography Applications

Commercial photoplethysmography (PPG) sensors and other biomedical devices that require near-infrared (NIR) light detection are limited by rigid photodetector architectures that cannot interface comfortably with skin. Flexible organic photodetectors could potentially solve this problem; however, organic photodetectors suffer from low NIR sensitivity, largely due to the early absorption cutoffs originating from the use of fullerene acceptors. This work details a new flexible organic photodiode (OPD) based on narrow bandgap non-fullerene-acceptor (NFA) bulk heterojunction (BHJ) incorporating a PTB7-Th and COTIC-4F blend. The photodetector developed for this study reaches an external an external quantum efficiency (EQE) to 60% in the 600-1000 nm range and responsivity (R) as high as approximate to 0.42 A W-1. Through the integration of a PEDOT:PSS and PDINO interfacial layers, undesired carrier injection is suppressed, and a detectivity (D*) in the order of approximate to 10(13) Jones is achieved. In addition, oxygen saturation and heart rate are successfully measured by integrating the developed photodiode in a PPG sensor.

Automated summary

This study developed a new flexible organic photodiode with improved sensitivity and performance in the near-infrared range by optimizing the structure and materials of the photodetector. By integrating the photodiode into a photoplethysmography sensor, oxygen saturation and heart rate were successfully measured.