Flexible Near‐Infrared Photoconductors Based on Donor‐Acceptor Organic Semiconductors

Organic photodetectors (OPDs) have attracted considerable attention for use in various sensing applications, including biomedical, imaging systems, and security surveillance. In particular, photoconductors (PCs) stand out due to their facile fabrication process and cost‐effective nature. However, achieving fast photo‐response PC using organic materials is still challenging. This study investigates the photo‐response of an organic bulk‐heterojunction (BHJ) device consisting of dithieno‐cyclopentathieno thiophene indone (PA940) as an acceptor and poly(benzothiadiazole) (PD2001) as a donor in 1:1 ratio, dissolved in o‐xylene. The BHJ organic photoconductor exhibits broad detection range from visible to near‐infrared (NIR). The detectivity is 2.65 × 10 11 and 2.26 × 10 11 Jones at 950 and 1070 nm, respectively, at 3 V with an incident optical power density of 100 µW cm −2 . The highest detectivity is obatined as 1.60 × 10 12 Jones at 1 µW cm −2 . In addition, rise/fall times of 5.5 ms/7.0 ms at 950 nm, and 4.7 ms/6.0 ms at 1070 nm, respectively, are observed using input power of 100 µW cm −2 . The BHJ OPCs on polyimide substrate show excellent flexibility, up to 5000 bending cycles with a bending radius of 2.5 mm. Therefore, the BHJ PCs can be applied to fast‐response, flexible NIR image sensors.