Design, Synthesis And Property Of D-A Polymers Containing Thiophene Unit

Energy problem and environmental problem have been bothering us, so scientists constantlypursue looking for clean and alternative to traditional fossil fuel energy. The solar energy as asubstitute energy is an effective route. And the polymer solar cells have been widely studied dueto low-cost, high flexible, solution processible. In this thesis, we synthesized a series of newpolymer materials by adjusting the bridging groups, changing the conjugated length andmodifying the donor unit and acceptor unit.1. Three novel conjugated copolymers containing a coplanarbithiophenevinyl-（2-pyran-4-ylidenemalononitrile）（TVM） unit linked with differentelectron-donating moieties （carbazole unit <triphenylamine unit <phenothiazine unit） weresynthesized via Heck polycondensation reactions. A double bond instead of a single bondbetween the TVM unit and the phenothiazine unit was incorporated compared with our previouswork PPTMT. By eliminating torsional interactions between donor and acceptor units,combination by double bonds resulted in an enhancement of the conjugated length, extension ofthe absorption spectral range and a low band gap of the polymers. The result showed the opticalabsorption of P3in the film exhibited a broader and approximately70-nm red-shifted absorption.Unfortunately, the HOMO energy level was accordingly increased which is unable for Voc.Bulk-heterojunction photovoltaic cells were fabricated with the copolymers as the donors and（6,6）-phenyl C71-butyric acid methyl ester （PC71BM） as the acceptor. The cells based on thethree copolymers exhibited power conversion efficiencies （PCEs） of0.36%,0.41%, and0.47%under one sun of AM1.5solar simulator illumination (100mV cm^-2).2. A relatively large and planar conjugated structure, high mobilitybenzo[1,2-b:4,5-b′]dithiophene donor unit （BDT） was used as the donor unit, and a very highelectron affinity tetrazine acceptor unit （TTz） was used as the acceptor unit.So two new D-Aconjugated polymers were synthesized by Stille cross–coupling polymerization. One thiophenebridge and two thiophene bridges are introduced between the TTz and BDT unit to improve the solubility of the copolymers and extend the spetra of the absorption, which facilitatedphotovoltaic device fabrication and got more light absorbed. The result shows the deep HOMOenergy level of-5.39eV and-5.28eV which is helpful for Voc. To investigate the photovoltaicproperties of the copolymers, bulk heterojunction PSCs with a structure of ITO/PEDOT:PSS/polymers: PC₇₀BM/ZnO/Al was fabricated. Here, ZnO NPs was used as cathode modifiedmaterial by taking place of LiF, the PCE was improved by50%. The power conversionefficiencies （PCE） of bulk heterojunction PSCs based on PBDT-1T-TTz and PBDT^-2T-TTzreached5.12%and5.0%, and the Voc of1.01V and0.93V, under one sun of AM1.5solarsimulator illumination (100mV cm^-2).