Synthesis And Properties Of Monothiophene Dye Sensitizer

Solar cell research has been the one hot spot of scientific research nowadays. Dye sensitized solar cells (DSSCs) brings new breakthroughs for the development of solar cell. The role of dye sensitizer in the DSSCs is to capture photons of light and transfer them into photogenerated electrons, the performance of dye sensitizer directly affects the overall the battery, which has become one of the most important points in DSSCs research field.The organic dye sensitizer mainly contains Donor (D); π (π-linker) and A (Acceptor). Any part of the D,π and A can be modified respectively. Modification of π-linker exerts a significant influence on the photo-electric conversion process in DSSCs. This paper designed and synthesized the D-x series dye sensitizers and the reference dyes T-x were also prepared, which all contain triphenylamine (TPA) moiety as electron donors and cyanoacrylic acid moiety as electron acceptors. The D-x series dyes consist of alkyl thiophene as π-conjugated linker. The relationship between the length of alkyl chain and the photovoltaic performance of dye sensitizers were investigated. T-x series consist of single thiophene, ethenyl thiophene and ethenyl benzene as π-conjugated linker. The influence of prolonging π-conjugated bridge to the photovoltaic performance of dyes and differences between thiophene and benzene in π-conjugated bridge were also examined. The main research contents are as follows:1. The D-x series dye sensitizers were designed and synthesized and T-x were synthesized as reference dyes. The target compounds and intermediates were characterized by MS, NMR, FT-IR etc. And then the photophysical properties, electrochemical properties, and photovoltaic properties of DSSCs based on two series of dyes were tested.2. On D-x series dye sensitizers, the UV-Vis absorption spectra showed that adding the alkyl chain on π-linker, the absorption band was occurred blue shift, and molar extinction coefficient decreased gradually. The cyclic volammetry (CV) curves showed that dyes’HOMO-LUMO levels were suitable for DSSCs. The results of photovoltaic performance indicated that PCE of D-2with methyl substituent (5.64%) is slightly higher than that of other dyes. With prolonging alkyl chains, the short-circuit photocurrent density (Jsc) decreased gradually, while open-circuit photovoltage(Voc) was improved.3. On T-x series dye sensitizers, the UV-Vis absorption spectra showed that, with prolonging π-conjugated bridge chain, the absorption spectra of T-2for ICT part appeared red-shifting and broadened15nm, but the absorption spectra of T-3for ICT part occurred blue-shifting. The Cyclic Volammetry (CV) curves indicated that T-x series dye sensitizers were suitable for DSSCs. The cyclic volammetry (CV) curves showed that thiophene as π-bridge was more effective for electronic transmission capacity than benzene ring. The results of photovoltaic performance indicated that T-3dye exhibited a satisfied efficiency of5.79%,(Jsc=12.41mA cm-2, Foc=0.69V and FF=0.68). The dye T-2showed low PCE due to the molecular aggregation on the surface of TiO2, which could be ascribed to its planar configuration.