Pollard Jennifer A, Zhang Dongshe, Downing Jonathan A, Knorr Fritz J, McHale Jeanne L
Department of Chemistry, Washington State University, Box 99164-4630, Pullman, Washington 99164-4630, USA.
J Phys Chem A. 2005 Dec 22;109(50):11443-52. doi: 10.1021/jp053595z.
Resonance Raman spectra are reported for Ru(4,4'-dicarboxylic acid-2,2'-bipyridine)2(NCS)2 (commonly called "N3") in ethanol solution and adsorbed on nanoparticulate colloidal TiO2 in ethanol (EtOH) and in acetonitrile (ACN), at wavelengths within the visible absorption band of the dye. Raman cross sections of free N3 in EtOH are found to be similar to those of N3 adsorbed on colloidal TiO2 in EtOH, and are generally lower than those of N3 on TiO2 in ACN. Strong electronic coupling mediated by surface states results in red-shifted absorption spectra and enhanced Raman signals for N3 adsorbed on nanocolloidal TiO2 in ACN compared to EtOH. In contrast, the absorption spectrum of N3 on nanocrystalline TiO2 in contact with solvent is similar for ACN and EtOH. Wavelength-dependent depolarization ratios for N3 Raman bands of both free and adsorbed N3 reveal resonance enhancement via two or more excited electronic states. Luminescence spectra of N3 adsorbed on nanocrystalline films of TiO2 and ZrO2 in contact with solvent reveal that the quantum yield of electron injection phi(ET) into TiO2 decreases in the order ACN > EtOH > DMSO. Dye-sensitized solar cells were fabricated with N3 adsorbed on nanocrystalline films of TiO2 in contact with ACN, EtOH, and DMSO solutions containing LiI/LiI3 electrolyte. Photoconversion efficiencies eta were found to be 2.6% in ACN, 1.3% in DMSO, and 0.84% in EtOH. Higher short circuit currents are found in cells using ACN, while the maximum voltage is found to be largest in DMSO. It is concluded that the increased photocurrent and quantum yield of interfacial electron transfer in acetonitrile as compared to ethanol and DMSO is primarily the result of faster electron injection of N3 when adsorbed on TiO2 in the presence of ACN as opposed to EtOH or DMSO.
报道了Ru(4,4'-二羧酸-2,2'-联吡啶)2(NCS)2（通常称为“N3”）在乙醇溶液中以及吸附在乙醇（EtOH）和乙腈（ACN）中的纳米颗粒胶体TiO2上时，在染料可见吸收带内波长处的共振拉曼光谱。发现EtOH中游离N3的拉曼截面与EtOH中吸附在胶体TiO2上的N3的拉曼截面相似，且通常低于ACN中TiO2上N3的拉曼截面。与EtOH相比，表面态介导的强电子耦合导致ACN中吸附在纳米胶体TiO2上的N3的吸收光谱红移且拉曼信号增强。相比之下，与溶剂接触的纳米晶TiO2上N3的吸收光谱对于ACN和EtOH是相似的。游离和吸附的N3的N3拉曼带的波长依赖性去极化率揭示了通过两个或更多激发电子态的共振增强。吸附在与溶剂接触的TiO2和ZrO2纳米晶薄膜上的N3的发光光谱表明，电子注入TiO2的量子产率φ(ET)按ACN > EtOH > DMSO的顺序降低。用吸附在与含有LiI/LiI3电解质的ACN、EtOH和DMSO溶液接触的TiO2纳米晶薄膜上的N3制备了染料敏化太阳能电池。发现光转换效率η在ACN中为2.6%，在DMSO中为1.3%，在EtOH中为0.84%。使用ACN的电池中发现短路电流更高，而最大电压在DMSO中最大。得出的结论是，与乙醇和DMSO相比，乙腈中界面电子转移的光电流和量子产率增加主要是由于在存在ACN而非EtOH或DMSO的情况下，N3吸附在TiO2上时电子注入更快的结果。
