Electronic Properties and Field-Effect Transistors of Oligomers End-Capped with Benzofuran Moieties



Three new oligomers bearing furan, thiophene, or bithiophene units end-capped by benzofuran moieties were synthesized and studied with respect to their structural, optical, electrochemical, and electrical properties. A comparison of the electronic properties performed by theoretical calculation, absorption and emission spectroscopy, and cyclic voltammetry revealed a strong influence of the spacer unit with a predominant impact on the emission spectra. Although both compounds with thiophene or bithiophene as central units presented relatively low quantum yields of 30 and 17 %, respectively, a maximum yield up to 71 % was measured for the compound based on a central furan core. High-vacuum-evaporated thin films were investigated by X-ray diffraction and AFM, before implementation as p-type semiconducting layers in organic field-effect transistors. Only derivatives with thiophene or bithiophene as central units presented a transistor activity, with mobilities up to approximately 1×10−2 cm2 V−1 s−1.