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Development of High‐Sensitivity Poly(2,7‐(9,9‐dioctylfluorene)‐alt‐5,5‐(4′,7′‐di‐2‐thienylbenzo [c][1,2,5]thiadiazole)) Thin‐Film‐Based Phototransistors by the Ribbon‐Floating Film Transfer Method

Alignment of polymer chains holds the key to the development of highly functional polymer‐based field‐effect transistors (FETs). The recently developed ribbon‐floating film transfer method (ribbon‐FTM) has the potential for development of polymer thin films with highly aligned chains, which are desirable for fabrication of efficient planar devices. These thin films consisting of well‐aligned polymer chains exhibit high degree of optical and electronic anisotropies. Herein, ribbon‐FTM‐processed thin‐film‐based organic photosensitive transistors of poly(2,7‐(9,9‐dioctylfluorene)‐alt‐5,5‐(4′,7′‐di‐2‐thienylbenzo [c][1,2,5]thiadiazole)) (PFO‐DBT) are reported. Under optimized fabrication conditions, polymer FETs based on PFO‐DBT demonstrate a charge carrier mobility of 0.002 cm2 V−1 s−1 and an on–off ratio of 5 × 104 under dark conditions. The devices further demonstrate a photosensitivity of ≈104 and 103 and a high responsivity of 8.37 and 4.6 A W−1 against green and red light illuminations, respectively. The results hold promise for the development of conducting‐polymer‐based high‐performance photosensitive organic field‐effect transistors (OFETs).