State Key Laboratory of New Ceramics & Fine Processing, Department of Material Science and Engineering, Tsinghua University, Beijing 100084, PR China.
Phys Chem Chem Phys. 2011 Apr 14;13(14):6416-22. doi: 10.1039/c0cp02704a. Epub 2011 Mar 8.
Room temperature ionic liquids (RTILs) have been used as electrolytes to investigate the anionic structure dependence of the photoelectrochemical responses of dye-sensitized solar cells (DSCs). A series of RTILs with a fixed cation structure coupling with various anion structures are employed, in which 1-methyl-3-propylimidazolium iodide (PMII) and I(2) are dissolved as redox couples. It is found that both the diffusivity of the electrolyte and the photovoltaic performance of the device show a strong dependence on the fluidity of the ionic liquids, which is primarily altered by the anion structure. Further insights into the structure-dependent physical properties of the employed RTILs are discussed in terms of the reported van der Waals radius, the atomic charge distribution over the anion backbones, the interaction energy of the anion and cation, together with the existence of ion-pairs and ion aggregates. Particularly, both the short-circuit photocurrent and open-circuit voltage exhibit obvious fluidity dependence. Electrochemical impedance and intensity-modulated photovoltage/photocurrent spectroscopy analysis further reveal that increasing the fluidity of the ionic liquid electrolytes could significantly decrease the diffusion resistance of I(3)(-) in the electrolyte, and retard the charge recombination between the injected electrons with triiodide in the high-viscous electrolyte, thus improving the electron diffusion length in the device, as well as the photovoltaic response. However, the variation of the electron diffusion coefficients is trivial primarily due to the effective charge screening of the high cation concentration.
室温离子液体（RTILs）已被用作电解质，以研究染料敏化太阳能电池（DSCs）的光电化学响应的阴离子结构依赖性。使用了一系列具有固定阳离子结构的 RTILs，与各种阴离子结构耦合，其中 1-甲基-3-丙基咪唑碘化物（PMII）和 I2 溶解为氧化还原对。结果发现，电解质的扩散率和器件的光伏性能都强烈依赖于离子液体的流动性，这主要是由阴离子结构改变的。进一步深入探讨了所采用的 RTILs 的结构依赖性物理性质，根据报道的范德华半径、阴离子骨架上的原子电荷分布、阴离子和阳离子的相互作用能，以及离子对和离子聚集体的存在情况进行了讨论。特别是，短路光电流和开路电压都表现出明显的流动性依赖性。电化学阻抗和强度调制光电压/光电流光谱分析进一步表明，增加离子液体电解质的流动性可以显著降低电解质中 I3-的扩散阻力，并减缓在高粘性电解质中注入电子与三碘化物之间的电荷复合，从而提高器件中的电子扩散长度以及光电响应。然而，由于高阳离子浓度的有效电荷屏蔽，电子扩散系数的变化微不足道。
