High-performance broadband organic photodetectors via water-transfer printing with biomedical monitoring capability

Abstract

This work reports a high-performance, broadband organic photodetector (OPD) fabricated via a water-transfer printing technique. By introducing a PM6:L8-BO bulk heterojunction (BHJ) active layer and employing water-transfer printing to construct a multilayer structure, the film morphology was significantly improved, leading to a notable reduction in dark current. Compared with conventional spin-coating methods, the device fabricated using water-transfer printing exhibited a specific detectivity of 4 × 10¹³ Jones at 830 nm in the near-infrared region, along with a larger linear dynamic range and faster response speed, demonstrating the clear advantages of this approach in device performance enhancement. Furthermore, the broadband OPD showed promising potential for biomedical applications. Integrated with photoplethysmography (PPG), the device enabled remote transmissive monitoring of heart rate and blood oxygen saturation, with SpO₂ values consistently maintained between 94% and 99%, within the normal physiological range. These results verify the feasibility and practicality of the device for remote health monitoring. This study presents a water-transfer printing strategy suitable for broadband OPDs, offering a technological route and research direction for their application in wearable medical devices.