Near-infrared OLEDs with high radiance of ∼105 mW Sr−1 m−2 for single-wavelength oxygen saturation detection

Abstract

Real-time in-home monitoring oxygen saturation (SpO2) is of great significance for early diagnosis and treatment of severe COVID-19, however, which should be based on multi-wavelength technology and complicated equipment. Herein, as a proof of concept, 740 nm is chosen as singlet light source for single-wavelength SpO2 detection, since absorbance differences between oxyhemoglobin (HbO2) and other interferences are the most rational. To controllably optimize excited-state characteristics of a near-infrared (NIR) thermally activated delayed fluorescence (TADF) emitters, an “extra conjugation” method is demonstrated by CNQP-TPA, whose 2,3-dicyanoquinoxaline phenanthroline (CNQP) acceptor forms strong intramolecular hydrogen bonds with two phenyls of triphenylamine (TPA) donors, which not only reduce excited-state relaxation-induced energy lose, but also provide more space for accurate modulation of intermolecular charge transfer (CT) interactions. As consequence, at the suitable doping concentration, CNQP-TPA endowed its device with a high radiance reaching ∼105 mW Sr−1 m−2 and desired electroluminescence peak at 744 nm. This device is further used as light source to detect SpO2 variation under single-wavelength mode. These results indicate the potential of NIR TADF materials and devices for in-home SpO2 monitoring and pre-diagnosis and prevention of severe COVID-19.