Department of Applied Chemistry, Graduate School of Engineering, Hiroshima University, Higashi-Hiroshima 739-8527, Japan.
Dalton Trans. 2019 Nov 12;48(44):16671-16678. doi: 10.1039/c9dt02600b.
Dithienosilole (DTS) and dithienogermole (DTG) are useful building units of π-conjugated organic materials. In the present work, donor-π-acceptor (D-π-A) dyes with bis(dihexyloxyphenyl)aminophenyl, DTS or DTG, and pyridine or cyanoacrylic acid as the donor (D), the π-conjugated linker (π), and the acceptor (A) units, respectively, were prepared and their optical properties were investigated. The D-π-A dyes exhibited strong absorption in the visible region, indicating efficient intramolecular donor-acceptor interaction. The addition of trifluoroacetic acid to solutions of pyridine-containing dyes led to red-shifts of the absorption bands as a result of pyridinium salt formation. Similar red-shifts were observed for cyanoacrylic acid dyes, which were due to the enhanced formation of neutral dyes relative to the separated ion pairs. The D-π-A dyes, however, showed similar absorption spectra when attached to the TiO2 surface, indicating that the dye-TiO2 electronic interaction was rather weak. In contrast to the finding that these dyes exhibited similar optical properties regardless of the π-linker (i.e., DTS or DTG), dye-sensitized solar cells (DSSCs) based on DTG-containing dyes exhibited superior performance compared to those based on DTS-containing dyes. Electrochemical impedance spectroscopy measurements supported the higher performance of the DSSCs with DTG-containing dyes.
二噻吩并[3,2-b:2',3'-d]噻吩（DTS）和二噻吩并[3,2-g:2',3'-d]锗（DTG）是有用的π-共轭有机材料的构建单元。在本工作中，制备了具有双（二己氧基苯基）氨基苯基、DTS 或 DTG 以及吡啶或氰基丙烯酸作为给体（D）、π-共轭连接体（π）和受体（A）单元的给体-π-受体（D-π-A）染料，并研究了它们的光学性质。D-π-A 染料在可见光区表现出强吸收，表明存在有效的分子内供体-受体相互作用。向含有吡啶的染料溶液中加入三氟乙酸会导致吸收带红移，这是由于形成吡啶𬭩盐所致。类似的红移也发生在氰基丙烯酸染料中，这是由于中性染料的形成相对于分离的离子对增强所致。然而，当 D-π-A 染料附着在 TiO2 表面上时，它们表现出相似的吸收光谱，这表明染料-TiO2 电子相互作用相当弱。与这些染料无论π-连接体（即 DTS 或 DTG）如何都表现出相似的光学性质的发现相反，基于含 DTG 染料的染料敏化太阳能电池（DSSC）的性能优于基于含 DTS 染料的 DSSC。电化学阻抗谱测量支持了含有 DTG 染料的 DSSC 具有更高的性能。
