Influence of the electrolyte cation in organic dye-sensitized solar cells: lithium versus dimethylimidazolium
Influence of the electrolyte cation in organic dye-sensitized solar cells: lithium versus dimethylimidazolium
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DOI：
10.1039/c0ee00223b
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发表时间：
2010-10
影响因子：
32.5
通讯作者：
Renzhi Li;Daxing Liu;Difei Zhou;Yushuai Shi;Yinghui Wang;Peng Wang
中科院分区：
文献类型：
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作者：
Renzhi Li;Daxing Liu;Difei Zhou;Yushuai Shi;Yinghui Wang;Peng Wang
我们研究了电解质阳离子如锂和二甲基咪唑对基于无金属发色团C218的染料敏化太阳能电池的光谱和电学特性的影响。通过电子吸收光谱和光电流作用光谱的测量，发现锂离子对C218染料包覆的纳米二氧化钛薄膜具有明显的红移效应。与二甲基咪唑相比，使用锂作为电解质阳离子引起C218敏化剂的激发态氧化还原电位的下移120 mV，并且纳米晶TiO 2膜的导带边缘的下移390 meV。在二氧化钛/染料界面处的能量对准中所产生的显着变化带来了不同的电子注入产率，如瞬态发射测量所揭示的。调制二氧化钛表面态分布与锂相对于二甲基咪唑诱导在介孔二氧化钛膜中的电子扩散系数略有下降。然而，二氧化钛上的锂阳离子的吸附强烈阻碍界面电荷复合相比，二甲基咪唑，有助于一个以上的数量级的增强的电子扩散长度。电子扩散长度的改善对电荷收集产率具有显著的影响，这也可以通过测量单色入射光子-电子转换效率来观察。需要进一步的界面工程来提高光伏和光电流，利用无金属有机染料的全部功率。
We investigate the influence of electrolyte cations such as lithium and dimethylimidazolium on the spectroscopic and electrical characteristics of dye-sensitized solar cells based on a metal-free chromophore C218. An evident bathochromic effect of lithium with respect to dimethylimidazolium is noticed for the C218 dye-coated nanocrystalline titania film via measuring electronic absorption and photocurrent action spectra. In comparison with dimethylimidazolium, the use of lithium as the electrolyte cation evokes a downward shift of the excited-state redox potential of the C218 sensitizer by 120 mV, and that of the conduction band edge of the nanocrystalline TiO2 film by 390 meV. The resultant remarkable variation in the energy alignment at the titania/dye interface brings on dissimilar electron injection yields as revealed by transient emission measurements. Modulating the titania surface states distribution with lithium relative to dimethylimidazolium induces a slightly declining electron diffusion coefficient in the mesoporous titania film. However, the adsorption of lithium cations on titania strongly retards the interfacial charge recombination compared to dimethylimidazolium, contributing to an over one order of magnitude of enhancement of electron diffusion length. The improvement of electron diffusion length has a noticeable effect on the charge collection yield, which can also be observed by measuring monochromatic incident photon-to-electron conversion efficiencies. Further interface engineering is needed to enhance both the photovoltage and photocurrent, making use of the full power of metal-free organic dyes.