High-Detectivity Wearable Organic Photodetectors for Self-Powered Pulse Rate and Oximetry Measurements

Wide-range light detection from the visible to the near-infrared (NIR) region is central to many applications such as high-speed digital cameras, autonomous vehicles, IR sensing, and wearable electronics. Recently, organic photodetectors (OPDs) were shown to be a promising platform for these applications. However, the conventional OPDs are often limited by low responsivity, narrow absorption range, large dark/noise current under applied bias, and large-scale production of these devices require halogenated processing solvents that have a negative environmental impact. In this talk, I will discuss strategies to reduce dark current in NIR OPDs based on a bulk heterojunction (BHJ) comprised of a polymer donor and a non-fullerene acceptor and the molecular design rule for processing OPDs from a green solvent, 2-methyltetrahydrofuran (2-MeTHF). Our OPDs exhibit an excellent specific detectivity (D*) over a broad wavelength range (400 -900 nm) and is comparable to those of commercial silicon-based photodiodes. We demonstrate that the PM7-D5:Y12 OPDs can be used as wearable self-powered devices to monitor heart rate and blood oxygen saturation.