Ultraflexible Near-Infrared Organic Photodetectors for Conformal Photoplethysmogram Sensors

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

    Research output: Contribution to journalArticle

    39 Citations (Scopus)


    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-pyridyl[2,1,3]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.

    Original languageEnglish
    JournalAdvanced Materials
    Publication statusAccepted/In press - 2018 Jan 1



    • Flexible photodetectors
    • Mechanical conformability
    • Near infrared photodetectors
    • Regioregular polymers
    • Ultrathin photonic devices

    ASJC Scopus subject areas

    • Materials Science(all)
    • Mechanics of Materials
    • Mechanical Engineering

    Cite this

    Park, S., Fukuda, K., Wang, M., Lee, C., Yokota, T., Jin, H., Jinno, H., Kimura, H., Zalar, P., Matsuhisa, N., Umezu, S., Bazan, G. C., & Someya, T. (Accepted/In press). Ultraflexible Near-Infrared Organic Photodetectors for Conformal Photoplethysmogram Sensors. Advanced Materials. https://doi.org/10.1002/adma.201802359