Preparation Of High Transparency PEDOT Counterelectrode And Its Application In Dye-sensitized Solar Cells Cells

Dye-sensitized solar cells（DSSCs）have drawn many attentions due to their easy-fabrication,high stability,and environmental friendliness.The DSSCs fabricated as bifacial cells can collect the energy from solar irradiation and ground reflection simultaneously.As a consequence,the power output of DSSC is further improved.For high-performance bifacial dye-sensitized cell,counter electrode needs to be highly transparent and the electrolyte layer is less absorptive.It is therefore necessary to optimize the electrolyte composition and screen the electrode materails.Compared with the high-cost platinum electrode,poly（3,4-ethylenedioxythiophene）（PEDOT）has the advantages of high conductivity,high catalytic activity,adjustable transparency,and low cost.These make it suitable for fabricating bifacial DSSCs.In this thesis,controlled electro-polymerization of 3,4-ethylenedioxythiophene（EDOT）on FTO conductive glass was achieved using a triangular wave AC current signal.By controlling the polymerization time,PEDOT counter electrodes with different transmittance are obtained.When the AC polymerization time is less than 4 s,the the PEDOT electrode shows transmittance exceeding over Pt electrode.SEM and AFM results show that an island hierarchical structure of the PEDOT deposited on the FTO surface.Cyclic voltammetry and impedance analysis show that the PEDOT electrode fabricated by the electro-polymerization for more than 2 s exhibits a lower interface charge transfer resistance compared with Pt electrode.This conclusion can be drawn from both cobalt complex and copper complex electrolyte system.It indicates that the PEDOT electrodes prepared in this work are featured as both high transmittance and high catalytic activity.When the transparent PEDOT electrodes are applied to zinc stannate based DSSCs,the resultant devices with cobalt complex and copper complex electrolytes yield open-circuit voltage of 970 m V and 1135 m V and photoconversion efficiencies of 6.95%and 4.77%,respectively.Furthermore,bifacial DSSCs were fabricated by combining the transparent PEDOT electrode with zinc tin oxide and titanium dioxide photoanodes.The current-voltage curves and impedance analyses show that the PEDOT electrode outperforms the Pt electrode when serving as the counter electrode in bifacial dye-sensitized cells.This is attributed to its high transparency and high catalytic activity.Since cobalt complex electrolyte absorbs less visible light than copper complex electrolyte,bifacial DSSC with cobalt complex electrolyte achieved a higher device efficiency.After optimization,the bifacial device constitued by a PEDOT electrode from 4 s electro-polymerization,a Ti O₂photoanode,and cobalt complex electrolyte yields the efficiencies of 8.80%,8.11%,and 11.38%for the front side,rear side,and bifacial irradiation,respectively.