Highly efficient flexible cathodes for dye sensitized solar cells to complement Pt@TCO coatings

Abstract

Solution-processed, semi-transparent, conductive electrodes based on PEDOT:PSS [poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)] using silver grids were developed on a plastic support. The flexible electrode (flextrode) was employed as a cathode in dye sensitized solar cells (DSSCs) and acts in two-fold manner: the PEDOT layer will yield a high surface area for effective electrocatalysis, while the silver grid will decrease the series resistance to rival transparent conducting oxide (TCO) coatings. DSSCs fabricated with Y123 dye and the developed cathodes show power conversion efficiencies of 7%, which are comparable to the reference device (6.9%) using Pt@FTO (F-doped SnO₂) coatings on glass under the same conditions. A flexible and cost effective electrode will help to penetrate the market for DSSCs and hybrid-organic–inorganic photovoltaics. Electrochemical impedance spectroscopy and modelling results confirm similar values of the series resistance and charge transfer resistance of the cathodes both in Pt-based and PEDOT-based cells, as well as the limited impact on the I–V curve from the modification of the charge transfer parameters in the PEDOT-based cells.