Synthesis And Optoelectronic Properties Of Small Organic Molecules Based On Benzo[1, 4]thiazino[2,3-b]phenothiazine

As vital technologies converting solar energy into electricity, dye-sensitized solar cells and organic solar cells have been the most attractive research fields due to their advantages of low cost and environmentally friendly.The structures, principles, related materials as well as the development of dye-sensitized solar cell and bulk heterojunction solar cells are reviewed in this thesis.Three novel dyes with benzo[1,4]thiazino[2,3-b]phenothiazine as core and?-conjugated bridge,p-hexyloxy benzene as donor, cyanoacrylate as acceptor, have been designed and synthesized according to the designing principles;Besides, based on the concept that different acceptor units may adjust the LUMO levels of small molecules to different extent,we have also synthesized four small organic molecular donors, which are composed of benzo[1,4]thiazino[2,3-b]phenothiazine as the centre,donor and ?-conjugated bridge,thiophene as ? linkage, 3-ethyl rhodanine or n-octyl-cyanoacrylate as acceptor.These seven small molecules have good solubility in common organic solvents(such as dichloromethane, chloroform and acetonitrile), which is benefitial for device fabrication.In addition, the optoelectronic properties of the two series of small molecules have been characterized as followings:(1) It can be learned that the LUMO and HOMO energy levels of three novel dyes match well with the oxidation potential of I-/I3- and the conduction energy level of TiO2 from UV-vis absorption spectrum and cyclic voltammetry, respectively. The power conversion efficiencies of DSSCs based on the three novel dyes are 3.67%, 3.55% and2.92%,corresponding to the sequence of DC6, DC8 and DC12,which indicates that the length of alkyl chain on N atom can make differences on the performance of DSSCs.Limited adsorption capacity on TiO2, poor conjugation and large steric hindrance may collaboratively result in the general efficiencies of DSSCs.(2) The four small organic molecular donors have broad absorption in the region of300-700 nm according to the UV-vis absorption spectrum.Then combined with cyclic voltammetry, it can be concluded that the LUMO and HOMO energy levels of the four small molecules match well with that of PCBM. By introducing different acceptor unit, the LUMO energy levels and bandgaps can be tuned finely.The bandgaps of four small molecules are narrow with the values around 1.75 eV.All of the above demonstrates that the four small molecules are promising donor materials for BHJ solar cells.