Ultraflexible Near‐Infrared Organic Photodetectors for Conformal Photoplethysmogram Sensors |
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Authors: | Sungjun Park Kenjiro Fukuda Ming Wang Chulhyo Lee Tomoyuki Yokota Hanbit Jin Hiroaki Jinno Hiroki Kimura Peter Zalar Naoji Matsuhisa Shinjiro Umezu Guillermo C Bazan Takao Someya |
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Affiliation: | 1. Center for Emergent Matter Science, RIKEN, Wako, Saitama, Japan;2. Thin‐Film Device Laboratory, RIKEN, Wako, Saitama, Japan;3. Japan Science and Technology Agency, PRESTO, Kawaguchi, Saitama, Japan;4. Departments of Chemistry and Biochemistry, University of California, Santa Barbara, CA, USA;5. Electrical and Electronic Engineering and Information Systems, The University of Tokyo, Tokyo, Japan;6. Department of Modern Mechanical Engineering, Waseda University, Shinjuku‐ku, Tokyo, Japan |
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Abstract: | Flexible organic optoelectronic devices simultaneously targeting mechanical conformability and fast responsivity in the near‐infrared (IR) region are a prerequisite to expand the capabilities of practical optical science and engineering for on‐skin optoelectronic applications. Here, an ultraflexible near‐IR responsive skin‐conformal photoplethysmogram sensor based on a bulk heterojunction photovoltaic active layer containing regioregular polyindacenodithiophene‐pyridyl2,1,3]thiadiazole‐cyclopentadithiophene (PIPCP) is reported. The ultrathin (3 µm thick) photodetector exhibits unprecedented operational stability under severe mechanical deformation at a bending radius of less than 3 µm, even after more than 103 bending cycles. Deliberate optimization of the physical dimensions of the active layer used in the device enables precise on/off switching and high device yield simultaneously. The response frequency over 1 kHz under mechanically deformed conditions facilitates conformal electronic sensors at the machine/human interface. Finally, a mechanically stretchable, flexible, and skin‐conformal photoplethysmogram (PPG) device with higher sensitivity than those of rigid devices is demonstrated, through conformal adherence to the flexuous surface of a fingerprint. |
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Keywords: | flexible photodetectors mechanical conformability near infrared photodetectors regioregular polymers ultrathin photonic devices |
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