Molecular doping of near-infrared organic photodetectors for photoplethysmogram sensors

Abstract
Doping is a common strategy in the field of semiconductor technology but its employment in organic photodetectors (OPDs) has been limited due to the typical uncontrollable increase of the dark currents. This study introduces three different molecular dopants, including p-type tris(pentafluorophenyl)borane, n-type benzyl viologen, and (4-(1,3-dimethyl-2,3-dihydro-1H-benzoimidazol-2-yl)-phenyl)dimethylamine, for near-infrared poly[[2,5-bis(2-hexyldecyl)-2,3,5,6-tetrahydro-3,6-dioxopyrrolo[3,4-c]pyrrole-1,4-diyl]-alt-[3′,3′′-dimethyl-2,2′:5′,2′′-terthiophene]-5,5′′-diyl]:[6,6]-phenyl C61butyric acid methyl ester (PMDPP3T:PC61BM) bulk-heterojunction OPDs. The results show that OPDs with optimal 0.02 wt% dopants exhibit low dark current (3.18 × 10−8A cm−2), high detectivity (5.56 × 1012Jones), and good environmental stability for ∼2 months. These doped OPDs are further used for pulse wave monitoring, which exhibit stable waveforms and can distinguish slow and fast heartbeat rates.

Citation
Wang, B., Scaccabarozzi, A. D., Wang, H., Koizumi, M., Nugraha, M. I., Lin, Y., … Someya, T. (2021). Molecular doping of near-infrared organic photodetectors for photoplethysmogram sensors. Journal of Materials Chemistry C, 9(9), 3129–3135. doi:10.1039/d0tc05549b

Acknowledgements
This work was financially supported by a collaborative research program (OSR#4196) between the University of Tokyo (UTokyo) and King Abdullah University of Science and Technology (KAUST) and Japan Science and Technology Agency (JST) ACCEL (grant no. JPMJMI17F1). We thank Dr Sixing Xiong (Riken, Japan) for the helpful discussion.

Publisher
Royal Society of Chemistry (RSC)

Journal
Journal of Materials Chemistry C

DOI
10.1039/d0tc05549b

Additional Links
http://xlink.rsc.org/?DOI=D0TC05549B

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