HOPV12 - Blogs

4 th Hybrid and Organic Photovoltaic Conference -Uppsala 2012 265
C127 - Investigation of TiCl4 treatment on carrier dynamics in solid-state dyesensitized
solar cells studied by time-resolved spectroscopy
Arianna Marchioro a , Amalie Dualeh b , Michael Grätzel b , Jacques-Edouard Moser a
a, EPFL , EPFL SB ISIC LPI GR-MO, Lausanne, 1015, CH
b, EPFL , EPFL SB ISIC LPI, Lausanne, 1015, CH
Solid-state Dye-Sensitized solar cells (ssDSCs) are a promising and challenging alternative to
conventional liquid DSCs based on volatile and/or corrosive liquid electrolytes.(1) Although
these systems, which use organic hole-transport materials (HTM) such as spiro-OMeTAD, are
now reaching 7% PCE,(2) additional efforts need to be invested in order to reach the same
efficiencies as their liquid equivalent.
It has been observed that the cell efficiency, both for liquid and solid devices, is increased
by an additional treatment by TiCl4, which modifies the metal-oxide semiconductor surface.(3)
The actual effect of this fabrication step on the solid-state cell and the mechanism involved,
however, are still unclear.
Based on kinetic studies obtained by femtosecond and nanonsecond transient absorption
spectroscopy, this surface treatment was shown to affect the dynamics of all charge carriers in
the cell compared to non-treated films: electron injection into the TiO2 following light
excitation, hole injection from the oxidized state of the dye into the hole transport material
and charge recombination.
Herein, we propose a model describing the interaction at the interface between TiO2, the
dye-sensitizer and spiro-OMeTAD. Results also emphasize the importance of controlling the
contact at the heterojunction between the HTM and the sensitized semiconductor.
References
[1] Bach, U.; Tachibana, Y.; Moser, J.-E.; Haque, S. A.; Durrant, J.R.; Grätzel, M.; Klug, D.R. "Charge Separation in
Solid-State Dye-Sensitized Heterojunction Solar Cells". J. Am. Chem. Soc. 121, 7445-7446 (1999).
[2] Burschka, J.; Dualeh, A.; Kessler, F.; Baranoff E.; Cevey-Ha, N.-L.; Yi, C.; Nazeeruddin, M.K. and Grätzel, M. "Tris(2-
(1H-pyrazol-1-yl)pyridine)cobalt(III) as p-Type Dopant for Organic Semiconductors and Its Application in Highly
Efficient Solid-State Dye-Sensitized Solar Cells" J. Am. Chem. Soc. 133, 18042-18045 (2011).
[3] Sommeling, P. M.; O'Regan, B. C.; Haswell, R. R.; Smit,H. J. P.; Bakker, N. J.; Smits, J. J. T.; Kroon, J. M. and J. A. M.
van Roosmalen "Influence of a TiCl4 Post-Treatment on Nanocrystalline TiO2 Films in Dye-Sensitized Solar Cells". J.
Phys. Chem. B, 110. 19191-19197 (2006).
© SEFIN 2012