Fully Inkjet‐Printed, Flexible TIPS‐Pentacene Photodetector for Photoplethysmogram

Organic photodetectors (OPDs) have emerged as promising candidates for non‐invasive medical monitoring and wearable optoelectronic devices, attributed to their cost‐effectiveness, adjustable optoelectronic properties, excellent performance, and solution‐processible fabrication techniques. Interestingly, no fully inkjet‐printed photodetector based on 6, 13 ‐ bis (triisopropylsilylethynyl) pentacene (TIPS‐pentacene) has been reported. Here, an inkjet‐printed OPD utilizing TIPS‐pentacene for a photoplethysmogram is introduced. The flexible photodetector with 200 µm channel length exhibits a high photo‐to‐dark current ratio over 9.6 × 10 2 , a responsivity of 0.23 A W −1 , and a detectivity of 1.8 × 10 11 Jones under 532 nm illumination (8.2 µW cm −2 ) at 5 V bias, achieves through systematic optimization of channel length, illumination intensity, and applied bias, and demonstrates fast photoresponse speed of 0.22 sec (rise) and 0.46 sec (decay). At a lower intensity of 1.1 µW cm −2 , the OPD demonstrates an improved responsivity of 0.54 A W −1 and detectivity of 4.2 × 10 11 Jones, indicating its capability to detect weak‐light signals. This device maintains strong photodetection performance, showing a 53.7% reduction in photocurrent at a severe bending radius of 1 cm. It is successfully demonstrated real‐time heart rate monitoring, which highlighted the practical applicability of the fabrication approach for wearable applications. By investigating the photoresponse behavior, this study establishes a foundation for advancing printed OPDs for low‐power, low‐cost, biomedical, and wearable electronics.