Ultraflexible Integrated Organic Electronics for Ultrasensitive Photodetection

Abstract Flexible organic photodetectors can form seamless contact with human skin, enabling continuous health monitoring. However, developing flexible photodetectors with high detectivity remains challenging because of the high theoretical dark current of photodetectors using a bulk heterojunction (BHJ) structure. Herein, a simple approach is reported that integrates a field‐effect transistor (FET) and an organic photodiode (OPD) module on the same substrate to achieve an ultralow dark current density (3.0 × 10 −8 mA cm −2 ), ultrahigh detectivity (1.7 × 10 15 Jones), and excellent flexibility. In the integrated sensor, the light‐sensing process occurs in the OPD module, whose signal is used to control the gate of the FET where the current output process occurs, enabling to utilize the light‐sensing properties of the OPD's BHJ structure while bypassing its high dark current. The ultraflexible integrated sensor amplifies the photoplethysmogram signal intensity from the OPD module by a factor of ≈10, thereby confirming its potential as an indoor wearable biosensor.