Effects of the polymethine chain length on the spectral response of dye sensitized devices

Abstract

In a dye sensitized (DS) devices, the working principle is based on the excitation and injection of electrons in the dye molecules. Due to the narrower spectral response of the dyes used as the sensitizer in the DS devices, the efficiency of the DS solar cells remains low, which is a major drawback in popularizing and commercializing DS solar cells. Therefore, the study of spectral response broadening methods applicable to DS devices is vital. In general, when synthesizing novel dyes, long carbon chains have been used to absorbed infrared radiation. In this study, cyanine dye molecules containing carbon chains of different chain lengths were used to observe the variations in the spectral response of the DS structures. Four cyanine dye derivatives, with different carbon ligands were investigated under the configuration, n-D-p structure. TiO2 was used as the n-type semiconductor, and the CuSCN was used as the p-type semiconductor, representing the n and p in the above configuration respectively. The device sensitized with the dye containing the longest central polymethine chain have shown a red shift in the spectral response threshold, extending up to ~900 nm. Additionally, the other dye molecules with shorter carbon ligands have a lesser extension in the spectral response.