Nanofibrous TiO 2 improving performance of mesoporous TiO 2 electrode in dye-sensitized solar cell
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RESEARCH PAPER
Nanofibrous TiO2 improving performance of mesoporous TiO2 electrode in dye-sensitized solar cell Marke´ta Zukalova´ • Ladislav Kavan • Jan Procha´zka • Arnosˇt Zukal • Jun-Ho Yum Michael Graetzel
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Received: 12 November 2012 / Accepted: 4 April 2013 / Published online: 27 April 2013 Ó Springer Science+Business Media Dordrecht 2013
Abstract A method of direct coating of conducting glass by electrospinning was developed. Electrospun fibrous TiO2 consisting of closely packed anatase nanocrystals of 40–50 nm in size was incorporated into mesoporous TiO2 thin film stabilized by phosphorus. The mesoporous framework formed by walls with 5–6 nm TiO2 nanocrystals surrounding 20 nm mesopores exhibits extreme porosity and consequently limited number of necking points. TiO2 with fibrous morphology was found to solidify mesoporous titania and to be beneficial for the performance of corresponding photoanode in dye-sensitized solar cell (DSC). Obviously, its wire-like structure suitably interconnects mesoporous network and thus increases the electron collection efficiency from the TiO2 layer to the F-doped SnO2 electrode. The solar conversion efficiency of a DSC employing optimized photoanode Special Issue Editors: Juan Manuel Rojo, Vasileios Koutsos This article is part of the topical collection on Nanostructured Materials 2012 M. Zukalova´ (&) L. Kavan J. Procha´zka A. Zukal J. Heyrovsky´ Institute of Physical Chemistry, v.v.i, Academy of Sciences of the Czech Republic, Dolejsˇkova 3, 18223 Prague 8, Czech Republic e-mail: [email protected] J.-H. Yum M. Graetzel Laboratory of Photonics and Interfaces, Institute of Chemical Sciences and Engineering, Swiss Federal Institute of Technology, 1015 Lausanne, Switzerland
consisting of nanocrystalline fibrous bottom layer, four mesoporous layers, and one nanocrystalline anatase scattering top layer sensitized with the N945 dye reached 5.35 %. This represents an improvement of about 9 % compared to the solar conversion efficiency of a DSC employing purely mesoporous TiO2 layer prepared by means of phosphorus doping (5.05 %). Keywords Dye-sensitized solar cell Titanium dioxide Nanofibers Mesoporous structure
Introduction The dye-sensitized solar cell (DSC, Graetzel cell) presents an attractive alternative to solid-state photovoltaics at competitive cost (Gra¨tzel 2001; Hagfeldt et al. 2010; Hardin et al. 2012; Kalyanasundaram 2010). Among various tasks to enhance the performance of DSC, the search for the best morphology of semiconductor photoanode is one of the key research targets (Kavan 2010, 2012). We have recently found beneficial properties of two-dimensional titania nanosheets (Laskova et al. 2012). In a subsequent work (Fan et al. 2012) reported on further improvement of the performance of 2D titania in a composite with another nanosheet (graphene), albeit the enhancement of DSC efficiency was observed only in narrow region of graphene concentrations around 0.75 wt% (Fan et al. 2012). On the other hand, hierarchical
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