Synthesis Of D-D-π-A Dyes And Their Application In Dye Sensitized Solar Cells

Dye-Sensitized Solar Cells (DSSCs) has attracted intense attention due to their easily fabrication, simple structures, low costs, no pollutions and high efficiency. As an important part of DSSCs, sensitizers have a great influence on absorbing light and turning solar energy to electrical energy. Therefore, the development of novel sensitizers has been a research issue in the field. In recent years, D-π-A dyes have been reported widely. However, D-D-π-A dyes have not been studied systematically. Especially the dyes with two electron donors at 2-position and 5-position of thiophene have never been reported so far.In this article, we designed dyes S-TPA, B-TPA, LS-TPA and LB-TPA. These dyes contain mono-triphenylamine or bis-triphenylamine with either alkyl chains or not as electron donor, C=C bond between 2-position and 3-position of thiophene as π bridge, and cyanoacrylic acid as electron acceptor.The structures, optical properties and electrochemical properties of dyes S-TPA, B-TPA, LS-TPA and LB-TPA have been investigated. These dyes have good absorption in UV-vis region, and the values of HOMO and LUMO are appropriate to be applied in DSSCs. The DSSCs based on dyes S-TPA and LS-TPA achieved a solar-to-electrical energy conversion efficiency of 2.83%(Jsc=8.96 mA·cm-2, Voc=0.59 V,ff=0.54) and 3.77%(Jsc=9.78 mA·cm-2,Voc=0.56 V,ff=0.69), respectively. The DSSCs based on dyes B-TPA and LB-TPA achieved a solar-to-electrical energy conversion efficiency of 6.06%(Jsc=14.21 mA·cm-2, Voc=0.62 V,ff=0.69) and 3.06%(Jsc=8.06 mA·cm-2, Voc=0.56 V,ff=0.67), respectively. These results indicated that our D-D-π-A structure which based on the novel π bridge can be used as optoelectronic materials, because it can lower the band gap of dyes for adding two donors; The DSSCs based on dyes without alkyl chains linking to electron donors can achieve a good solar-to-electrical energy conversion, because the size of dyes can influence effective absorption on TiO2.