Samsung Advanced Institute of Technology

Photomultiplication organic photodetectors (PM-OPDs) demonstrate exceptional sensitivity in low-light environments, making them valuable for imaging, environmental monitoring, and wearable health sensors. However, traditional PM-OPDs require significantly high operational voltages, which lead to elevated dark current and degrade sensitivity and noise performance. To address these limitations, we introduce a novel light-mediated PM-OPD that enhances signal gain through a cycle of light emission and reabsorption within the active layers. This design integrates emission and absorption layers, achieving an external quantum efficiency exceeding 200% while maintaining a low dark current (~10？？ A/cm²) and high detectivity over 5×10¹³ Jones. By reabsorbing internally generated light to drive photomultiplication, the device enables efficient amplification without noise penalties. It achieves a 29.5 dB gain in photoplethysmography (PPG) signal detection at 10 lux and demonstrates scalability for cost-effective production using thermal evaporation, making it a promising solution for low-power, high-sensitivity wearable sensors.