Polymer and Color Chemistry Program, North Carolina State University, Raleigh, NC 27695, USA.
Phys Chem Chem Phys. 2013 Jun 7;15(21):8401-8. doi: 10.1039/c3cp51260f. Epub 2013 Apr 29.
Two new heteroleptic Ru(II) bipyridyl complexes MH06 and MH11 were designed, synthesized and characterized for DSSCs. While the ancillary ligand of MH06 was molecularly engineered with a strong electron donating group coupled with an extended π-conjugated system, the ancillary ligand of MH11 contained a longer π-conjugated system only. Molecular modeling, photophysical, and photovoltaic properties were compared under the same experimental conditions against the benchmark N719. In an effort to understand the structure-property relationship, their photovoltaic and photoelectrochemical properties including Jsc, Voc, ground and excited state oxidation potentials, UV-Vis absorption, and molar extinction coefficients were studied. The UV-Vis results showed intense MLCT absorption peaks of MH06 and MH11 in the visible region with a red shift of 12 and 18 nm, respectively, with significantly higher molar extinction coefficients compared to N719. Tetrabutylammonium (TBA) substituted MH11-TBA demonstrated the most efficient IPCE of over 90% in the plateau region covering the entire visible spectrum and extending into the near IR region (ca. 890 nm), which showed a solar-to-power conversion efficiency (η) of 10.06%, significantly higher than that of the benchmark N719 dye (9.32%). The superior performance in terms of the IPCE and Jsc of MH11 can be attributed to the bulky and highly hydrophobic nature of the pyrene-based ancillary ligand, which behaves as a shielding barrier for hole-transport recombination between TiO2 and the electrolyte. In addition, the IMPS results showed that the contribution of dyes to the conduction band shift of the TiO2 level is almost similar, regardless of different substitutions on the bipy-moiety. This implies that the open-circuit photovoltage (Voc) increases with reduced charge recombination in the presence of a thick layer of tetrabutyl ammonium ions (TBA) of the dye anchored on the surface of TiO2.
两种新的异双核钌（II）联吡啶配合物 MH06 和 MH11 被设计、合成并用于 DSSC 进行了表征。而 MH06 的辅助配体通过与扩展的π共轭体系偶联进行了分子工程设计，具有很强的供电子基团，而 MH11 的辅助配体仅含有更长的π共轭体系。在相同的实验条件下，通过与基准 N719 进行比较，对其进行了分子模拟、光物理和光伏性能的比较。为了理解结构-性质关系，研究了它们的光伏和光电化学性质，包括 Jsc、Voc、基态和激发态氧化电位、紫外-可见吸收和摩尔消光系数。紫外-可见结果表明，MH06 和 MH11 在可见光区具有强烈的 MLCT 吸收峰，分别红移了 12 和 18nm，与 N719 相比，摩尔消光系数显著提高。四丁基铵（TBA）取代的 MH11-TBA 在整个可见光谱覆盖的平台区域表现出超过 90%的最高 IPCE，并且延伸到近红外区域（约 890nm），这表明太阳能到电力的转换效率（η）为 10.06%，明显高于基准 N719 染料（9.32%）。MH11 在 IPCE 和 Jsc 方面的优异性能可归因于基于芘的辅助配体的庞大和高度疏水性，其表现为 TiO2 和电解质之间空穴传输复合的屏蔽屏障。此外，IMPS 结果表明，无论在联吡啶部分上进行不同的取代，染料对 TiO2 能级导带位移的贡献几乎相似。这意味着在存在固定在 TiO2 表面的染料的四丁基铵（TBA）厚层时，开路光电压（Voc）增加，电荷复合减少。
