Optimizing the Energy Offset between Dye and Hole-Transporting Material in Solid-State Dye-Sensitized Solar Cells

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• 作者：Christian T. Weisspfennig ; Michael M. Lee ; Jo毛l Teuscher ; Pablo Docampo ; Samuel D. Stranks ; Hannah J. Joyce ; Hermann Bergmann ; Ingmar Bruder ; Dmitry V. Kondratuk ; Michael B. Johnston ; Henry J. Snaith ; Laura M. Herz
• 刊名：Journal of Physical Chemistry C
• 出版年：2013
• 出版时间：October 3, 2013
• 年：2013
• 卷：117
• 期：39
• 页码：19850-19858
• 全文大小：478K
• 年卷期：v.117,no.39(October 3, 2013)
• ISSN：1932-7455

文摘

The power-conversion efficiency of solid-state dye-sensitized solar cells can be optimized by reducing the energy offset between the highest occupied molecular orbital (HOMO) levels of dye and hole-transporting material (HTM) to minimize the loss-in-potential. Here, we report a study of three novel HTMs with HOMO levels slightly above and below the one of the commonly used HTM 2,2鈥?7,7鈥? tetrakis(N,N-di-p-methoxyphenylamino)-9,9鈥?spirobifluorene (spiro-OMeTAD) to systematically explore this possibility. Using transient absorption spectroscopy and employing the ruthenium based dye Z907 as sensitizer, it is shown that, despite one new HTM showing a 100% hole-transfer yield, all devices based on the new HTMs performed worse than those incorporating spiro-OMeTAD. We further demonstrate that the design of the HTM has an additional impact on the electronic density of states present at the TiO₂ electrode surface and hence influences not only hole- but also electron-transfer from the sensitizer. These results provide insight into the complex influence of the HTM on charge transfer and provide guidance for the molecular design of new materials.