Vertically stacked all-organic ring-shaped pulse oximetry sensor with ultra-low power consumption and low-luminance operation

Health monitoring with wearable pulse oximetry (PO) paves the way for personalized, point-of-care health management. Organic PO (OPO) sensors are particularly promising for wearable POs due to their excellent compatibility with flexible, lightweight form factors and design freedom, enabling low power consumption comparable to or even surpassing that of conventional inorganic systems. However, further power reductions are crucial for wearable systems with limited onboard power, and achieving sufficient signal strength at minimal luminance is essential for extended operation. Here, we propose an OPO structure with both ultralow power consumption and low luminance operation. By combining a ring-shaped, vertically stacked two-color organic light-emitting diode (OLED) with a circular organic photodiode (OPD) filling the interior and exterior of the OLED ring, we demonstrate OPO sensors requiring only a few μW to drive the OLEDs and operable at a few tens of cd/m2, demonstrating potentials for continuous health monitoring with extended long-term operation.