Non‐Contact Vitality Monitoring Enabled by Interface‐Modified Photomultiplication Organic Photodetectors

ABSTRACT Photomultiplication‐type organic photodetectors (PM‐OPDs) enable external quantum efficiencies (EQE) exceeding 100%, providing intrinsic signal amplification and simplified circuit integration. Such high sensitivity is essential for non‐contact physiological monitoring, where weak optical signals must be precisely detected over a distance. However, their practical use remains challenged by high dark current and sluggish response. Here, we introduce interface engineering using conjugated electrolytes (PFN‐Br, NDI‐Br) to simultaneously suppress dark current and tailor trap state distribution at the ZnO cathode interface. The champion ZnO/NDI‐Br device achieved a peak EQE of 6780% and a specific detectivity of 5.3 × 10 12 Jones at −20 V, along with ultrafast rise and fall times of 0.05/0.02 ms. These improvements originate from enhanced electron mobility and reduced interfacial traps, enabling efficient electron trapping and hole tunneling injections. Leveraging these advances, we demonstrated a non‐contact vital‐sign monitoring system capable of high‐fidelity heart rate detection at 50 cm and accurate blood oxygen saturation (SpO 2 ) measurement at 20 cm. This work establishes interface‐engineered PM‐OPDs as a promising platform for next‐generation remote medical sensing and long‐range optical detection.