Sensitive detection of near-infrared (NIR) light is applicable to variety of optical, chemical, and biomedical sensors. Of these diverse applications, NIR photodetectors have been used as a key component for photoplethysmography (PPG) sensors. In particular, because NIR organic photodetectors (OPDs) enable fabrication of stretchable and skin-conformal PPG sensors, they are attaining tremendously increasing interest in both academia and industry. Herein, we report strain-durable and highly sensitive NIR OPDs using an organic bulk heterojunction (BHJ) layer. For effective suppression of dark current, we employed BHJ combination consisting of PTB7-Th:Y6 which forms high energy barrier against transport-injected holes. The optimized OPDs exhibited high specific detectivity up to 2.2 × 1012 Jones at 800 nm. By constructing the devices on the parylene substrates, we successfully demonstrated stretchable NIR OPDs and high-performance skin-conformal PPG sensors.
This work was supported by a grant from the National Research Foundation of Korea funded by the Korean government (Ministry of Science and ICT) ( NRF-2021R1A2C1007304 , NRF-2020M3H4A3081822 , NRF-2020R1F1A1073564 , and NRF-2021R1A4A1033155 ). This research was also supported by Korea Electric Power Corporation (grant number R21XO01-20 ). This research was also supported by the MSIT (Ministry of Science and ICT), Korea, under the ITRC (Information Technology Research Center) support program(IITP-2021-2020-0-01461) supervised by the IITP (Institute for Information & communications Technology Planning & Evaluation).
