The design and synthesis of conjugated organic materials for electronic device applications

The growing demand for organic conjugated materials for their use in semiconductor devices requires the design and synthesis of new materials with advanced properties. For electronic and optoelectronic technologies, low band gap conjugated polymers and conjugated oligomers are among the most promising materials. The lack of stability of these materials and the complicated synthetic routes necessary for their preparation limit their potential application in electronic devices, however. This dissertation is devoted to the design and synthesis of some new conjugated polymers and oligomers, the development of new synthetic methodologies for conducting polymers, and the application of these materials in organic electronic devices. Several strategies in controlling the band gaps of conjugated polymers are explored. Furthermore, theoretical studies of these systems are compared with experimental results.; The novel approach of introducing imide acceptor moieties in conjugated polymers resulted in the preparation of n-type conducting polymers, such as poly(benzo[c]thiophene-N-2 ′-ethylhexyl-4,5-dicarboxylic imide (band gap ca 1.2 eV) which was further characterized by improved charge transport properties. Also, alternating the donor ethylenedioxythiophene with acceptor isobenzo[ c]thiophene-4,5-dicarboxylic imide units in one polymeric backbone yielded a push-pull conjugated copolymer, poly(3,4-ethylenedioxythiophene-co-isobenzo[ c]thiophene-N-2′-ethylhexyl-4,5-dicarboxylic imide) which was found to be the first stable processable, p,n-type low band gap (ca 1.0 eV) organic material. The application of these materials in electronic devices such as solar cells, field effect transistors and near-infrared electrochromic devices is also investigated.; The design and synthesis of two new series of the conjugated alkyl-chain endcapped oligofluorene-thiophenes and substituted pentacene derivatives are also described. Thin film field-effect transistor (TFT) devices made from select oligomers, 5,5′-bis-(7-hexyl-9H-fluoren-2-yl)-2,2 ′-bithiophene and 2,3,9,10-tetram ethylpentacene, for example, have shown remarkable stability and high performance (μ: 0.14 cm 2V−1s−1 and 0.30 cm 2V−1s−1, respectively with an on/off ratio >105).; Finally, an unprecedented solid-state polymerization of dihalogenthiophene derivatives was applied to the preparation of the industrially important conducting polymer—poly(3,4-ethylenedioxythiophene). This new synthetic strategy provides a unique opportunity for the fabrication of well-ordered, highly conductive organic films on non-conductive flexible surfaces, an important feature for creating all-organic lightemitting devices.