[18a-E102-1~11] 12.7 Biomedical Engineering and Biochips

▼ [18a-E102-2] Flexible Near-infrared Organic Photodetector with a Liquid Crystalline Phthalocyanine Derivative for Photoplethysmography

〇(D)Shahriar Kabir¹, Yukiko Takayashiki¹, Jun-ichi Hanna¹, Hiroaki Iino¹ (1.Tokyo Tech.)

Keywords:flexible electronics, near-infrared photodetector, liquid crystalline semiconductor

In this study, flexible near-infrared (NIR) organic photodetectors (OPDs) (device structure: PET/Al/PEIE/active layer/Ag) were prepared on 25 μm PET substrates with active layer of a liquid crystalline organic semiconductor 1,4,8,11,15,18,22,25-octaoctyl-phthalocyanine (8H₂Pc) and phenyl-C61-butyric acid methyl ester (PC₆₁BM). At -5 V reverse bias, the external quantum efficiency (EQE) and shot-noise-limited detectivity (D^*_sh) at NIR wavelength of 740 nm of the flexible OPD without any bending strain were 9% and 1.1×10¹¹ Jones, respectively. Measurements were also taken when the OPD was bent at a radius of 7.5 mm (thickness of the index finger of an average human subject). Even under strain, the device performed ideally with EQE of 5% and D^*_sh of 5.7×10¹⁰ Jones indicating very good mechanical flexibility and durability of the OPD. The potential of this device in vital signal monitoring was demonstrated by monitoring the photoplethysmogram of a human subject with a rigid NIR OPD in ambient conditions.