Highly transparent counter electrodes for dye-sensitized solar cells made with advanced nanocomposite materials

Abstract

Dye sensitized solar cells (DSSCs) constitute a good alternative for harnessing the solar energy since they are based on earth abundant nanocomposite materials, their manufacture requires simple chemical processes, which are more or less benign, and have low fabrication cost. DSSCs' efficiency has just reached 13% and there is even more room for improvement. Researchers are trying to improve each component and find the best combination of them which will lead to enhanced electrical characteristics and long term stability in order to proceed to their commercialization. Due to the nanostructured character of the materials used in DSSCs, they can be either opaque or even transparent. Transparent dye-sensitized solar cells can be integrated as photovoltaic windows replacing structural building elements. In particular, to this end, a large volume of the recent works on DSSC's is devoted to the study of structural properties of materials that can be used as negative electrodes and also be transparent. At the present work transparent nickel doped cobalt sulfide was fabricated on a SnO2:F electrode through chemical bath deposition and tested as an efficient electrocatalyst and as an alternative to the expensive platinum counter electrode. The advantage of the deposition method is that it doesn't require annealing at high temperature. The substitution of platinum with a nickel doped cobalt sulfide counter electrode in a DSSC affects the charge transfer resistance corresponding to the counter electrode/ electrolyte interface affecting its electrical parameters. In order to investigate how much this electrode could affect the electrical characteristics of a dye-sensitized solar cell, we manufactured cells with the same TiO2 photoanode sensitized with dye (N719) and employing the same quasi-solid electrolyte bearing a redox couple, altering only the counter electrode used. All cells were characterized through photocurrent-voltage measurements and electrochemical impedance spectroscopy (EIS).