Optimizing the energy offset between dye and hole-transporting material in solid-state dye-sensitized solar cells

Weisspfennig, C. T. et al. (2013) Optimizing the energy offset between dye and hole-transporting material in solid-state dye-sensitized solar cells. Journal of Physical Chemistry C, 117(39), pp. 19850-19858. (doi: 10.1021/jp405734f)

Abstract

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′,7,7′- tetrakis(N,N-di-p-methoxyphenylamino)-9,9′-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.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Docampo, Dr Pablo
• Authors: Weisspfennig, C. T., Lee, M. M., Teuscher, J., Docampo, P., Stranks, S. D., Joyce, H. J., Bergmann, H., Bruder, I., Kondratuk, D. V., Johnston, M. B., Snaith, H. J., and Herz, L. M.
• College/School: College of Science and Engineering > School of Chemistry
• Journal Name: Journal of Physical Chemistry C
• Publisher: American Chemical Society
• ISSN: 1932-7447
• ISSN (Online): 1932-7455
• Published Online: 03 September 2013