Synthesis And OFET Property Of Multi-branched Styryl Conjugated Materials

In order to explore new functional materials, investigate the effect of multi-branched degree and molecular shape on the optoelectronic properties and search for three-dimensional organic semiconductors. Our main studies are summarized as follows.1. Three benzofuran-based compounds 1,4-bis[2-(benzofuran-2-yl)vinyl]benzene(2BFVB) with linear shape, 1,3,5-tris[2-(benzofuran-2-yl)vinyl]benzene(3BFVB) with star shape and 1,2,4,5-tetra[2-(benzofuran-2-yl)vinyl]benzene(4BFVB) with cruciform shape were synthesized through Wittig-Horner reaction. 2BFVB adopt a two-dimensional herringbone packing motif and there are two kinds of molecule conformations. The crystal packing of 3BFVB is more sensitive to the crystallization condition. Two single-crystal phases and one thin-film phase were found. 3BFVB(?-phase) molecules pack into a three-dimensional cofacial herringbone structure. 4BFVB forms an inter-inserted two-dimensional hexagon packing. The molecular shape and aggregate packing exert remarkable effects on the optoelectronic properties. The quantum yield of 2BFVB is very high either in the solution(74%) or in the crystalline solid state(76%). The high solid emission efficiency of 2BFVB is possibly related to the two molecule conformations in the herringbone-arranged H-aggregates. Both 2BFVB and 3BFVB display hole-transport ability. The performance of 3BFVB amorphous film is nearly equal to that of its crystalline film, which would be helpful to simplify the device fabrication. This study shows that the substitution degree exerts drastic effects on the solubility, polymorphism, crystal packing and optoelectronic properties.2.Three benzothiophene-based compounds 1,4-bis[2-(benzothien-2-yl)vinyl]benzene(2BTVB) with linear shape, 1,3,5-tris[2-(benzothien-2-yl)vinyl]benzene(3BTVB) with star shape and 1,2,4,5-tetra[2-(benzothien-2-yl)vinyl]benzene(4BTVB) with cruciform shape were synthesized through Wittig-Horner reaction. The molecular shape exerts marked effects on the thermal stability, film morphology and optoelectronic properties. Compounds 2BTVB and 3BTVB are thermally stable before the melting point. In contrast, 4BTVB solid is decomposed upon heating. Single-crystal structure analyses show that 3BTVB molecules pack into a three-dimensional cofacial herringbone structure. In comparison with 2BTVB and 4BTVB, both the absorption and emission spectra of 3BTVB display a blue-shift feature. This is possibly related to the discontinued π-conjugation through meta-substitution. The evaporated film of 2BTVB is high crystalline. In contrast, 3BTVB molecules pack disorderly in the evaporated film. The molecular shape and film morphology exert remarkable effects on the carrier-transport ability.