Design and synthesis of perylenediimide, naphthalenediimide based n-type organic semiconducting polymers, small molecules : Fabrication of high performance organic field - effect transistors

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Four new n-channel naphthalene diimide (NDI) and perylene diimide (PDI) copolymers (NDI-Ph, NDI-BT, PDI-Ph, and PDI-BT) were synthesized and their solution processed organic thin film transistor (OTFT) devices fabricated. These copolymers possess crystalline domains, annealing their films induced crystalline phases in the thin film structures with a very high degree of enhancement in crystallinity. Remarkable enhancements in the electron transport behavior for all the four copolymers were achieved on improving the intermolecular interactions in their thin film structures. The intermolecular interactions in the thin film state on the macro scale, facilitating improved and higher charge carrier transport in annealed devices as compared to the as-spun devices that have lesser crystalline phases. These copolymers demonstrated electron mobility enhancement of several orders and are reported to be as high as 0.8 cm2 V−1 s−1 and 0.2 cm2 V−1 s−1 with Ion/Ioff ratios 105 for NDI-Ph and NDI-BT, while those of PDI-Ph and PDI-BT are 0.04 cm2 V−1 s−1 and 0.032 cm2 V−1 s−1, respectively, with Ion/Ioff ratios of 103−104.
Supervisor: Parameswar Krishnan Iyer