Preparation and ionic transport properties of conductive polymers for dye-sensitized solar cells
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This work aims to improve the components of the dye-sensitized solar cells (DSSCs) which are a type of photovoltaics that consist mainly of a photoanode, a counter electrode, a light sensitive molecule (sensitizer) and an electrolyte solution that regenerates the solar cell through a redox system. The improvement of the DSSC focuses on the material used for the counter electrode. Usually, it is made out from platinum sputtered on a conductive glass. However, platinum is an expensive metal that is hard to manipulate and can be corroded by the mediator. In this perspective, an alternative material for the expensive platinum is investigated which is the conductive polymer poly(3,4-ethylenedioxythiophene) (PEDOT). This polymer has a structure that promotes high ionic and electronic conductivities, and it can be doped with different anions (e.g. PSS, perchlorate). PEDOT was synthesized chemically and electrochemically. Its chemical structure was characterized by FTIR. The electrochemical behavior of PEDOT was assessed by cyclic voltammetry (CV). The catalytic activity of PEDOT towards the redox system proved to be higher than the activity of the platinum. In addition to the experimental approach, modelling of the ionic-electronic conductivity of PEDOT was performed based on the Nernst-Planck-Poisson and the Butler-Volmer formalisms, and the simulation outputs were fitted to the experimental data. In the last step, the conductive polymer PEDOT was used as a counter electrode to fabricate DSSCs. The cells were characterized through electrochemical impedance spectroscopy (EIS) and through current-voltage (J-V) curves. The based PEDOT cells demonstrated an efficiency of 8.1%, which was higher than the based-platinum solar cells (6.3%).
