A detailed investigation of the effect of hole transport material (HTM) pore filling on the photovoltaic performance of solid-state dye-sensitized solar cells (ss-DSCs) and the specific mechanisms involved is reported. It is demonstrated that the efficiency and photovoltaic characteristics of ss-DSCs improve with the pore filling fraction (PFF) of the HTM, 2,2',7,7'-tetrakis-(N, N-di-p-methoxyphenylamine)9,9'-spirobifluorene(spiro-OMeTAD). The mechanisms through which the improvement of photovoltaic characteristics takes place were studied with transient absorption spectroscopy and transient photovoltage/photocurrent measurements. It is shown that as the spiro-OMeTAD PFF is increased from 26% to 65%, there is a higher hole injection efficiency from dye cations to spiro-OMeTAD because more dye molecules are covered with spiro-OMeTAD, an order-of-magnitude slower recombination rate because holes can diffuse further away from the dye/HTM interface, and a 50% higher ambipolar diffusion coefficient due to an improved percolation network. Device simulations predict that if 100% PFF could be achieved for thicker devices, the efficiency of ss-DSCs using a conventional rutheniumdye would increase by 25% beyond its current value. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledged KAUST grant number(s): KUS-C1 - 015-21
Acknowledgements: J. M.-K. and I.-K. D. contributed equally to this work. This publication was partially based on work supported by the Center for Advanced Molecular Photovoltaics (Award No KUS-C1 - 015-21) made by King Abdullah University of Science and Technology (KAUST). A. M., A. P., N. T., M. G., and J.-E. M. are grateful to the Swiss National Science Foundation for financial support. We thank Dr. Robin Humphry-Baker for his experimental assistance with transient photovoltage/photocurrent measurements, Dr. Shaik M. Zakeeruddin for providing Z907 dye, Manuel Tschumi for fabricating TiO2 films, and George Y. Margulis for providing absorption data used in Section 2.6.
This publication acknowledges KAUST support, but has no KAUST affiliated authors.