Infrared Organic Photodetectors Employing Ultralow Bandgap Polymer and Non-Fullerene Acceptors for Biometric Monitoring

Abstract
Recent efforts in the field of organic photodetectors (OPD) have been focused on extending broadband detection into the near-infrared (NIR) region. Here, two blends of an ultralow bandgap push-pull polymer TQ-T combined with state-of-the-art non-fullerene acceptors, IEICO-4F and Y6, are compared to obtain OPDs for sensing in the NIR beyond 1100 nm, which is the cut off for benchmark Si photodiodes. It is observed that the TQ-T:IEICO-4F device has a superior IR responsivity (0.03 AW-1 at 1200 nm and -2 V bias) and can detect infrared light up to 1800 nm, while the TQ-T:Y6 blend shows a lower responsivity of 0.01 AW-1 . Device physics analyses are tied with spectroscopic and morphological studies to link the superior performance of TQ-T:IEICO-4F OPD to its faster charge separation as well as more favorable donor-acceptor domains mixing. In the polymer blend with Y6, the formation of large agglomerates that exceed the exciton diffusion length, which leads to high charge recombination, is observed. An application of these devices as biometric sensors for real-time heart rate monitoring via photoplethysmography, utilizing infrared light, is demonstrated.

Citation
Jacoutot, P., Scaccabarozzi, A. D., Zhang, T., Qiao, Z., Aniés, F., Neophytou, M., Bristow, H., Kumar, R., Moser, M., Nega, A. D., Schiza, A., Dimitrakopoulou-Strauss, A., Gregoriou, V. G., Anthopoulos, T. D., Heeney, M., McCulloch, I., Bakulin, A. A., Chochos, C. L., & Gasparini, N. (2022). Infrared Organic Photodetectors Employing Ultralow Bandgap Polymer and Non-Fullerene Acceptors for Biometric Monitoring. Small, 2200580. Portico. https://doi.org/10.1002/smll.202200580

Acknowledgements
A.A.B and P.J. would like to thank the Royal Society for financial support. M.N, H.B, M.M., and I.M. acknowledge financial support from KAUST, including Office of Sponsored Research (OSR) awards no. OSR-2019-CRG8-4086 and OSR-2018-CRG7-3749. The authors acknowledge funding from ERC Synergy Grant SC2 (610115), the European Union's Horizon 2020 research and innovation programme under grant agreement n°952911, project BOOSTER and grant agreement n°862474, project RoLA-FLEX, as well as EPSRC Project EP/T026219/1. The authors A.D.S and T.D.A would like to thank the ALBA synchrotron and staff for their help with the GIWAXS measurements. The authors acknowledge the King Abdullah University of Science and Technology (KAUST) for financial support.

Publisher
Wiley

Journal
Small

DOI
10.1002/smll.202200580

PubMed ID
35246948

Additional Links
https://onlinelibrary.wiley.com/doi/10.1002/smll.202200580

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