Article pubs.acs.org/JPCC
Chemical Effects of Tin Oxide Nanoparticles in Polymer ElectrolytesBased Dye-Sensitized Solar Cells Hwaseok Chae,†,§ Donghoon Song,†,§ Yong-Gun Lee,† Taewook Son,† Woohyung Cho,† Yong Bum Pyun,† Tea-Yon Kim,† Jung Hyun Lee,† Francisco Fabregat-Santiago,‡ Juan Bisquert,‡ and Yong Soo Kang*,† †
Department of Energy Engineering and Center for Next Generation Dye-sensitized Solar Cells, Hanyang University, Seoul 133-791, Korea ‡ Photovoltaic and Optoelectronic Devices Group, Department de Física, Universitat Jaume I, 12071 Castelló, Spain S Supporting Information *
ABSTRACT: The effects on the photovoltaic performance of the incorporation of SnO2 nanoparticles into the polymer of a solid-state dye-sensitized solar cell (DSC) based on the poly(ethylene oxide)/poly(ethylene glycol) dimethyl ether solid electrolyte are studied in this paper. It has been found that the addition of SnO2 nanoparticles to the solid electrolyte produces several key changes in the properties of the solid-state DSC that produced a better performance of the device. Therefore, we have measured an improvement in electrolyte conductivity by a factor of 2, a linear rise in the TiO2 conduction band position, a reduction in the electron recombination rate, and a decrease in charge-transfer resistance at the counterlectrode/electrolyte interface. All these improvements produced an increase in the power conversion efficiency from 4.5 to 5.3% at 1 sun condition, a consequence of the increase of both Voc (oc = open circuit) and Jsc (sc = short circuit) without any sacrifice in FF (fill factor). The origin of these changes has been associated to the strong Lewis acidic character of SnO2 nanoparticles yielding to the formation of a I3− percolation layer for holes at the surface of SnO2 and the reduction of the concentration of free I3− and K+ ions inside the pores of TiO2. From these results, it is concluded that the physicochemical effects of inorganic nanofiller in the polymer electrolyte may also be considered a good route in designing the high efficiency solid-state DSCs employing the polymer electrolyte.
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INTRODUCTION Since the development of dye-sensitized solar cells (DSCs), they have received great attention as a promising technology as a low cost energy source of the next photovoltaic generation.1 High energy conversion efficiency of over 12% has been reported for DSCs using a cobalt redox-based liquid electrolyte.2 However, the liquid electrolyte in DSCs has drawbacks, mostly stemming from solvent evaporation or leakage problems. Many academic studies have been focused on solid-state or quasi-solid-state alternatives utilizing hole transport materials,4−8 gel and solid polymer electrolytes.9−17 DSCs using a solid polymer electrolyte have many advantages associated with a solvent-free device such as improved thermal and long-term stabilities, higher environmental safety under breakage of the device, and so forth. © XXXX American Chemical Society
However, the use of solid polymer electrolyte, most commonly with poly(ethylene oxide) (PEO), has some drawbacks that make them less efficient than their liquid counterparts. The most important drawback is the low ionic conductivity, in the range from 10−7 to 10−5 S cm−1 at room temperature, and the low penetration of the PEO into the nanoporous titania electrode, which results in the insufficient utilization of dyes due to the poor interfacial contact between dyes adsorbed TiO2 surface and the solid polymer electrolyte.18 Special Issue: Michael Grätzel Festschrift Received: November 29, 2013 Revised: February 11, 2014
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dx.doi.org/10.1021/jp4117485 | J. Phys. Chem. C XXXX, XXX, XXX−XXX
The Journal of Physical Chemistry C
Article
in our previous paper.23 The SnO2 (
