| As a new kind of functional organic materials, oligothiophene is getting more and more attention because of it's excellent optical and electrical properties. With the aim of developing new properties and getting wider application of oligothiophene derivatives, new oligothiophene derivatives: 1,4-di(2′-thienyl)benzene(TPT), 5,5″-dicyano-2,2′:5′,2″-terthi- ophene(2CN-3T), 4,4"-dicarboxyl-5,5"-bipropyl-2,2':5',2"-terthiophene(2COOH-BP3T), 5,5″- biformyl-2,2′:5′,2″-terthiophene (2CHO-3T), 5,5″′-dicyano-2,2′:5′,2″:5″,2″′-tetrathiophene (2CN-4T), 2,3′:4′,2″-terthiophene(V-3T), 5,5″-dicyano-2,3′:4′,2″-terthiophene(2CN-V-3T), 2,3,4,5-tetra(2′-thienyl)thiophene(X-5T), 2,5-di[(5′-cyano)thiophene-yl]-3,4-di(2′-thienyl)thi- ophene(2CN-X-5T), 2,5-di[(5′-formyl)thiophene-yl]-3,4-di(2′-thienyl)thiophene(2CHO-X- 5T), 2,5-dithienyl-3,4-di[(2, 2')dithiophene-5-yl]thiophene(X-7T) and 2, 5-di(5′-formylthienyl) -3,4-di(5″-formyl-4,2′:5′,2″-dithienyl)thiophene(4CHO-X-7T), were synthesized and charactered by MS, NMR, IR, and HPLC. Their properties of optical and electrical were studied. Their potential application in organic electrochromic and organic solar cell were investigated.Photophysical and electrochemical properties of the compounds were measured by UV-Vis absorption spectra, fluorescence spectra and cyclic voltammetry, based on which the relationship between molecular structure and optical, electrical properties were studied. Changing the length of conjugated chain and the introduction of electron-donating groups or electron withdrawing groups can control the optical, electrical properties of oligothiophene derivatives.Based on the optical and electrical properties, the application of oligothiophene derivatives as electrochromic materials and organic photovoltaic materials were investigated. In the two different system: electrochromic active layer/ electrolyte solution and electrochromic active layer/conducting gel (or conducting filter), the clectrochromic properties of oligothiophene derivatives were studied. Three electrochromic devices were fabricated. Device A is ITO(indium tin oxide)/electrochromic active layer/ electrolyte solution/Pt. In ITO/OHC-3T-CHO/conducting gel/ITO device (device B), the ITO-coated glass was serviced as the electrode, electrolyte was conducting gel. Although ITO/OHC-3T-CHO/conducting filter paper/ITO device (device C) and device B was similar, the electrolyte was different. The electrolyte of device C was conducting filter paper. Based on device A, the clectrochromic properties of 2CN-3T, 2CHO-3T, 2COOH-BP3T, 2CN-4T, 2CH3O-4T, V-3T, 2CN-X-5T, poly(TPT), poly(3T) and poly(5T) solid films were investigated, and the electrochromic mechanisms also be discussed. It was found that these oligohtiophene derivatives exhibited reversible, clear colour change on electrochemical doping and dedoping. 2CHO-3T solid film based on device B showed reversible, clear color change from yellow to bright green on electrochemical doping and dedoping, and poly(3T) based on device B exhibited reversible, clear colour change from yellowish orange to navy blue on electrochemical doping and dedoping. Similiar to ITO/OHC-3T-CHO/conducting gel/ITO, the ITO/OHC-3T-CHO/conducting filter paper/ ITO device (device C) exhibited colour change from yellow to green on electrochemical doping and dedoping.Potovoltaic devices, using ITO, Al as electrode, X-5T, X-7T, 2CN-V-3T, 2CN-X-5T, 4CHO-X-7T as electron donor, PTCDA as accepter, were fabricated. Differential scanning calorimetry(DSC) and X-ray diffraction(XRD) measurements show that the vacuum- evaporated X-5T film is crystalline, while X-7T film is amorphous. Crystalline may be contributed to enhancement performance characteristics of device by promoting forward interfacial electron transfer and eliminating the subconducting band trap sites. The ITO/X-5T/PTCDA/Al device indeed has better performance characteristics than the photovoltaic device based on X-7T. In addition, ITO/4CHO-X-7T/PTCDA/Al has higher open circuit voltage (Voc) than the device using X-7T as electron donor. It is possible that intermolecular hydrogen bonding between 4CHO-X-7T and PTCDA contributes to the enhancement by promoting forward interfacial electron transfer.
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