Strain-durable dark current in near-infrared organic photodetectors for skin-conformal photoplethysmographic sensors

Summary

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 × 10 ¹² 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.

Graphical abstract

Highlights

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  Significant reduction of dark current was achieved from PTB7-Th:Y6 NIR OPDs

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  The developed OPD exhibited strain-durable dark current

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  OPDs efficiently operated on ultra-thin substrates

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  Skin-conformal PPG sensors were demonstrated based on the developed OPDs

Abstract

Applied sciences; Sensor; Wearable computing