Simple oligothiophene-based dyes with a cyanoacrylic acid anchor were synthesized and evaluated as a photosensitizer for dye-sensitized solar cells (DSSCs). Although the molecular properties of the dyes at a glance are quite similar to those of related oligothiophene dyes with a carboxylic acid anchor, the DSSC performance of the former (up to η = 4.8%) is fairly improved over the latter (≈1.2%). Absorption spectra of the oligothiophene dyes with the cyanoacrylic acid are red-shifted compared to those with the carboxylic acid, resulting in the improved photocurrent conversion efficiency at above 600 nm in the DSSCs. With the aid of theoretical calculations, electronic properties of the oligothiophene dyes were investigated, and it turned out that the excited states of the dyes are significantly affected by the anchoring groups. The cyanoacrylic acid anchor brings about a stabilized LUMO with localized electron density on the cyanoacrylic acid moiety, whereas the carboxylic acid dye has relatively a high-lying LUMO with delocalized electron density over the oligothiophene moiety. Thus, the difference in the DSSC performance is rationalized by the different electronic structure at the excited states caused by the anchoring groups on the oligothiophene cores.
我们合成了具有
氰基
丙烯酸锚的简单低聚
噻吩基
染料,并将其作为
染料敏化太阳能电池(DSSC)的光敏剂进行了评估。虽然这些
染料的分子特性与具有
羧酸锚的相关低聚
噻吩染料十分相似,但前者的 DSSC 性能(η = 4.8%)比后者(≈1.2%)有相当大的提高。与含有
羧酸的低聚
噻吩染料相比,含有
氰基
丙烯酸的低聚
噻吩染料的吸收光谱发生了红移,从而提高了 DSSC 在 600 纳米以上波长的光电流转换效率。借助理论计算研究了低聚
噻吩染料的电子特性,结果发现
染料的激发态受到锚定基团的显著影响。
氰基
丙烯酸锚基带来了稳定的 LUMO,电子密度集中在
氰基
丙烯酸分子上,而
羧酸染料的 LUMO 相对较高,电子密度分散在低聚
噻吩分子上。因此,低聚
噻吩核上的锚定基团导致激发态的电子结构不同,从而合理地解释了 DSSC 性能的差异。