A Flexible Sensitive Visible-NIR Organic Photodetector with High Durability

Low-cost, deformable visible-near-infrared (visible-NIR) photodetectors can be configured into non-planar shapes to meet emerging optical needs. However, it remains challenging to develop low-cost flexible visible-NIR photosensor with excellent mechanical deformability and high optical detectivity. Herein, we report a flexible visible-NIR organic photodetector (OPD) based on a blend film of D18:BTP-4F as the active layer on a polyethylene naphthalate substrate. Owing to the low exciton binding energy of BTP-4F and the preferred orientation of the D18:BTP-4F film, the as-fabricated OPD exhibits excellent self-powered optoelectronic performances with a high responsivity, high detectivity, and fast response time of 206 mA W⁻¹, 6.45 × 10¹² Jones (1 Jones = 1 cm Hz^1/2 W⁻¹), and 9 µs at the wavelength of 800 nm and bias voltage of 0 V, respectively. After 1000 bending/releasing cycles with an angle of 150° at a radius of curvature of 3 mm, the current-voltage curves remain stable both measured under dark and light illumination, indicating obvious device operation robustness. The reliable linear photosensitivity of the as-obtained OPD is demonstrated by the photoresponse under a range of different incident light intensities and its practical application for wearable health monitoring such as heart rate measurement is well demonstrated. Furthermore, a flexible visible-NIR image sensor for imaging acquisition is shown by demonstrating 5 × 5 OPD array under 850 nm light irradiation. The collective results on blend film design, flexible device fabrication and characterization, and imager development shed light on sought-after visible-NIR photosensing and imaging systems.