Ultraflexible Near‐Infrared Organic Photodetectors for Conformal Photoplethysmogram Sensors. Issue 34 (8th July 2018)

• Record Type: Journal Article
• Authors: Park, Sungjun; Fukuda, Kenjiro; Wang, Ming; Lee, Chulhyo; Yokota, Tomoyuki; Jin, Hanbit; Jinno, Hiroaki; Kimura, Hiroki; Zalar, Peter; Matsuhisa, Naoji; Umezu, Shinjiro; Bazan, Guillermo C.; Someya, Takao
• Is Part Of: Advanced materials. Volume 30:Issue 34(2018)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2018-07-08
• Subjects: flexible photodetectors -- mechanical conformability -- near infrared photodetectors -- regioregular polymers -- ultrathin photonic devices; Materials -- Periodicals; Chemical vapor deposition -- Periodicals; 620.11
• DOI: 10.1002/adma.201802359
• Languages: English
• ISSNs: 0935-9648

Abstract

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‐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 10 3 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. Abstract : An ultraflexible near‐infrared (IR) organic photodetector that simultaneously exhibits both high speed (response frequency > 1 kHz at −3 dB) and small bending radius ( r = 3 μm) is developed. Stable charge carrier transport is exhibited when the device is attached to a curved and/or folded part of the human skin, enabling a fingerprint conformal photoplethysmogram sensor.