Conjugated Polymers of Rylene Diimide and Phenothiazine for n-Channel Organic Field-Effect Transistors

A series of new n-type copolymers based on perylene diimide (PDI) or naphthalene diimide (NDI) and phenothiazine (PTZ) with different side chain length and molecular weight have been designed and synthesized by Pd-catalyzed Suzuki coupling polymerization with or without phase-transfer catalyst Aliquat 336. The effects of main chain, side chain, and molecular weight on the thermal, optical, electronic, and charge transport properties of the polymers have been investigated. Aliquat 336 improves molecular weight as well as reduces polydispersity index of the polymers. All the polymers exhibit a broad absorption extending from 300 to 900 nm. The main chain and side chain structure and molecular weight have minor effects on the HOMO (-5.8 to -5.9 eV) and LUMO (-3.7 to -3.8 eV) levels of the polymers. n-Channel field-effect transistors with bottom-gate top-contact geometry based on these copolymers exhibit electron mobilities as high as 0.05 cm(2) V-1 s(-1) and on/off ratios as high as 10(5) in nitrogen, which are among the best reported for rylene diimide-based polymers under the same test conditions.