Synthesis And Characters Of π-conjugated Donor-Acceptor Materials

The organic optoelectronic functional materials and devices have attracted great interest by academia and industry as a result of their huge potential applications. Many organic molecular devices have been studied in detail, such as organic light-emitting diode, organic filed effect transistor, organic photovoltaic cell and organic laser. The partial properties of these devices have been up or over those of the inorganic semiconductor devices. In fact, the huge development of science and technology is depended on the excellent properties of molecular material, and the properties of molecular materials are crucial to the performance of the photoactive and electroactive devices. Therefore, it is most interest to design and synthesize novel organic semiconductor materials with excellent properties. Donor-acceptor (D-A) organic molecule is one of the most important conjugated organic materials, which have attracted much academic and technological research interest. In these compounds the electron-donating and electron-accepting groups are connected through aπ-conjugated linker. Tuning different donor moiety or acceptor moiety in a D-A molecule would modify its physical and chemical properties.A novel family ofα-Cinnamoyl Cyclic Ketene Dithioacetals (CCKDA) derivatives with asymmetrical structure (D-π-A) in a simple and low-cost way by Claisen-Schmidt condensation reactions between the donor-containing aldehydes and the electron-withdrawing (CCKDA). The advantage of this method is the relative high yield as well as the high purities. The crystal structure of molecule displays the non-planar molecular structure and a J-aggregation packing style which should be beneficial to high luminescence efficiencies. The UV-vis absorption and photoluminescence of these compounds suggest significant intramolecular charge-transfer (ICT) behaviour between the donor and acceptor. The electrochemical properties indicate that these compounds have relative high electron transport ability. Quantum-chemical calculation to the theoretical model confirms the ICT transition mechanism of this system. The properties of the electroluminescence (EL) demonstrate that these compounds can be good candidates for the emitting layer in organic light-emitting diodes (OLED).Three fluorescent materials functionalized with D-π-A-π-D structures have been synthesized and characterized. Introduction of different donor moieties decreases the band gaps allowing a fine-tuning of the optical and electrical properties. The photophysical properties are of a significant ICT behaviour and solvatochromism. The double layers electroluminescent devices were fabricated by using these molecular materials as light emitting layer. In additional, The bulk heterojunction solar cells using these compounds as donors and PCBM as acceptor were fabricated. The results clearly show that the ICT transition contributes to the photoresponse and the relationship between the photovoltaic properties and the molecular structure are clearly analyzed. When the D-A materials are used as donors for solar cells, if the donor moiety has intensive conjugated structure and the acceptor has strong electron-withdrawing ability, the absorption could cover most of the visible spectral region and good film-forming ability could be obtained. Then a solar cell with high energy conversion efficiency could be expected.Novel dendritic conjugated molecules with D-π-A-π-D structures have been designed and synthesized. The acceptor is based on (phenylsulfonyl)benzene which may have high electron-affinity. The optimized structure of compounds by calculation displays the non-planar molecular structure which should be beneficial to improve luminescence efficiencies. The UV-vis absorption and photoluminescence of these compounds suggest significant ICT behaviour between the donor and acceptor. The new fluorescent derivative might be potent fluorophore candidates for organic optoelectronic devices.