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.

Ambient‐Stable Near‐Infrared Organic Photodetectors with Ultrahigh Detectivity and Ultrafast Response for Biometric Monitoring

“…The clear resolution of the PPG signal of these PDs made it easier to read the signal, potentially benefitting the applicability to blood pressure monitoring. [ 28 ] When irradiating with light from the 950‐nm LED, the OPD allowed the detection of the heartbeat even through the wavelength was at the absorption edge of the PM6:Y6 film. We integrated the OPD with a microcontroller board [(Arduino) UNO], a lithium‐ion battery (3.7 V, 405 080), an LED, and an organic LED (OLED) display (SSD1306) to realize a portable PPG device (Figure 7c).…”

Recent Advances in Smart Organic Sensors for Environmental Monitoring Systems

“…143 Because of their natural flexibility, organic materials may also be useful for health monitoring and biometric authentication through direct contact with human skin. 144,145 Song et al investigated infrared organic photodiodes using a doping compensation strategy. 146 An organic compound, Y6, was introduced as a second acceptor into PTB7-Th:COTIC-4F blends, where it suppressed nonradiative recombination near the energy gap induced by COTIC-4F (Figure 11a).…”

Electron-donating amine-interlayer induced n-type doping of polymer:nonfullerene blends for efficient narrowband near-infrared photo-detection

“…Solution-processable blends of electron donating (D) and accepting (A) organic semiconductors with high photon-to-charge conversion efficiency have potential for low-cost and high-performance photodetectors for visible and near-infrared (NIR) wavelengths 1 , 2 . Especially in the NIR, there is growing interest with applications in, for instance, biometric monitoring 3 , night vision imaging, medical diagnostics, and quality control in agriculture 4 – 7 . In the recent years, synthetic efforts to lower the optical gaps of organic semiconductors has resulted in NIR-absorbing polymers 3 , 8 – 13 and nonfullerene acceptors (NFA) 14 – 18 which, when applied in broadband NIR organic photodetectors (NIR-OPD), reach specific detectivities (D*) on the order of 10 12 Jones, approaching those of commercial silicon or indium gallium arsenide (InGaAs) inorganic detectors at room temperature, albeit in a limited wavelength range, up to 900–1200 nm (see refs.…”