Organic Photoplethysmography Sensor Based on Directional Emission Microcavity Organic Light‐Emitting Device

Abstract Wearable photoplethysmography (PPG) sensors provide real‐time monitoring of essential human health parameters by integrating a light source with a photodetector. However, they face a common challenge: the presence of a faint pulsating (AC) signal amidst a highly noisy and drifting non‐pulsatile background. This necessitates fine‐tuning how the light is spread out to make sure that a significant number of emitted photons carry vital physiological information and trigger the detector's photocurrent. An innovative organic PPG sensor with a microcavity organic light‐emitting diode (OLED) that emits light in a controlled direction, coupled with an annular organic photodetector (OPD) is demonstrated here. By adjusting the OLED's cavity lengths, the microcavity resonance peak is shifted, achieving angled directional emission. Placing the microcavity OLEDs at the center of the annular OPD enhances the portion of light that reflects from arterial vessels in the skin and tissues. This increases the AC signal for recording arterial vessel pulsations by 47.66%. This advancement simplifies sensor recognition and achieves an unprecedented low power consumption of only 9.96 µW for heart rate sensing, meeting essential recognition criteria.