Thiophene-Based Organic Sensitizers And Electrocatalytic Materials For Dye-Sensitized Solar Cells

Dye-sensitized solar cells (DSSCs) have attracted wide attention in scientific research for its low cost, simple fabrication process and power conversion efficiency. In this thesis, we have synthesized three new types of dyes as the sensitizer and prepared conductive polymer films and N,B-doped graphene materials as the counter electrode for use in DSSCs. The main results are summarized below:(1) We designed and synthesized two sensitizers based on dibenzothiophene as the π bridge, triphenylamine as the electron donor and cyano acetic acid as the electron acceptor. The presence of alkoxy chain can effectively inhibit dye aggregation and charge recombination, resulting in improved Foc·(2) We designed and synthesized two isomeric sensitizers (I1 and 12) based on 4,8-dithienylbenzo[1,2-b:4,5-b’]dithiophene in two perpendicular directions to build cross-conjugated systems. It was found that the charge transfer interaction was much stronger in the benzodithiophene direction (12) than the dithienylbenzene direction (II). As a result,12 produced much higher current and efficiency than I1.(3) Three isomeric dye sensitizers (HI, H2, H3) having double D-π-A branches linked with an akoxy chain have been designed and synthesized. Solar cell performance depended on the link position at the EDOT unit. Among the three isomers, H1 (two link sites near the donor) exhibited the highest efficiency (8.06%), H2 (one linke site near the donor while the other linke site near the acceptor) showed lower efficiency and H3 (two link sites near the acceptor) showed the lowest efficiency.(4) Liquid crystalline conductive polymer films were fabricated by electropolymerization of a bifunctional EDOT monomer linked with a vinyl imidazolium group. The molecular ordering in the liquid crystalline polymer film resulted in high carrier mobility and hence high electrocatalytic performance. When applied as the cathode of DSSCs, power conversion efficiency of 8.08% was achieved versus 7.69% for the Pt cathode.(5) N, B-doped graphene materials with high specific surface area were synthesized for use as the counter electrode in DSSCs. The electrocatalytic performance increased with the doping amount of B followed by a drop with further increasing the doping amount. The best N,B-doped graphene achieved power conversion efficiency of 8.09% versus 7.54% for the Pt cathode.