Synthesis of heterocyclic conjugated polymers and their applications in electronic devices

Abstract

We report here the synthesis via Suzuki polymerization of four novel alternating polymers containing 9,9-dioctylfluorene and electron-withdrawing bithiazole moieties, PHBTzF, PTHBTzTF, PT2HBTzT2F and F8BTz, and their application to electronic devices. The UV-vis. absorption and PL emission spectra of the polymers were measured to investigate their optical properties. Cyclic voltammetry experiment showed the improvement of n-doping stability of the polymers as well as the decrease of their LUMO energy levels as a result of bithiazole in the polymer main-chain. Moreover, it was found that band-gaps of the thiazole-based polymers were tuned by change of their HOMO energy levels rather than LUMO energy levels. Conventional PLED devices were fabricated in the configuration [ITO / PEDOT:PSS / polymer / Ca / Al] using the polymers as emitting layers. EL emission colors were also tuned from green to red by thiophene extension of the monomer. In addition, a preliminary organic solar cell device with the configuration [ITO / PEDOT:PSS / (PTHBTzTF+C60) / Ca / Al] and a preliminary organic thin-film transistor making use of PT2HBTzT2F as a p-type channel material were also fabricated and characterized. With the progress of organic electronics, materials possessing various functionalities are attracting much attention. Here we synthesized a novel photo-alignment polymer composed of conjugated carbazole main-chain and coumarin side-chain through nickel(0)-mediated polymerization. Carbazole is a well-known hole transporting material and coumarin is also famous for its good photo-alignment property. Photo-chemical reactivity of the coumarin side-chain was monitored by UV-vis. spectroscopy, and liquid crystal (LC) photo-alignment direction of the polymer film was proved to be perpendicular to the polarization direction of the irradiated UV light. The highest occupied molecular orbital (HOMO) level of the polymer, measured from both cyclic voltammetry and photoelectron spectrosc...