Photovoltaic Properties Of Oligo(Thiophene)s Derivatives And Synthesis & Characterization Of Photovoltaic Materials With Triphenylamine Units

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 over those of the inorganic semiconductor devices. In fact, the huge development of science and technology in the field of organic optoelectronic devices is depended on the excellent properties of molecular material and proper devices. Therefore, it is interesting to synthesize novel organic semiconductor materials with excellent properties and design devices with proper structures.Here we focused on two families of materials with multibranch chromophores. X-shape oligo(thiophene)s They were investigated by uv-vis, XRD, DSC et al. to show the optoelectronic properties of the films deposited under vacuum. The cells show betterg performance than the cell based on linear oligo(thiophene)s. Benefit for the excellent properties of the multibranch moleculars, we design and synthesize moleculars with triphenylamine units. They were investigated by uv-vis, fluorescence, electrical chemistry to show optoelectronic properties. They are proved to be donor materials by energy levels and fluorescence quenching by EP-PTC.The films of two X-shaped oligo(thiophene)s, 3,4-dibithienyl-2,5- dithienylthiophene (7T) and 2,5-dibithienyl-3,4-ditrithienylthiophene (11T), which are prepared by vacuum evaporation, have been investigated as novel electron donor layers in two-layer photovoltaic cells. UV-vis absorptions show red-shifted and broadened absorptions of the vacuum evaporated films to those of the corresponding solutions and spin-coating films which are beneficial for photovoltaic properties. X-ray diffraction (XRD) and differential scanning calorimetry (DSC) measurements show the vacuum-evaporated films are almost amorphous. Two-layer photovoltaic cells have been realized by thermal evaporation of 7T and 11T as donors and N,N'-bis(1-ethylpropyl)-3,4:9,10-perylene bis(tetracarboxyl diimide) (EP-PTC) as an acceptor. An energy conversion efficiency (ECE) of 0.18 % of the cell based on 7T under white light with irradiation of 100 mw/cm2 has been demonstrated by the measurements of current (I)- voltage (V) curves of the cells, which is better than the ECE of the reference system based on donor dihexylterthienyl (H3T) which is linear and withoutα,βlinkage. In an attempt to develop of 3D conjugated architectures to obtain new classes of organic photovoltaic materials, novel conjugated star shaped molecules with a triphenylamine as a core have been designed and synthesized. And carbzole, triphenylamine, phenothiazine and bithiophene are attached to the central core respectively. Owing to largeπconjugated system, the four compounds have red shifted absorptions than the similar systems without double bonds. Introduction of different donor moieties allow a fine-tuning of the optical and electrical properties. The maximum fluorescence wavelengths of the four compounds are red-shifted, when the polarities of solvents are increased. There may be TICT states functioning in different solvents of the molecules with triphenylamines and bithiophenes outsides. The analysis of electronic chemistry properties and fluorescence quenchinges show that the compounda are proper donors when doped with EP-PTC acceptor. It is interesting to investigate the relations between the configuration of the molecules and their properties. Therefore we can give advices to design new materials.