Research On Properties Of Dye-sensitized Solar Cells From Co-Pt Alloy Counter Electrodes

Dye-sensitized solar cell (DSSC) is a new kind of solar cell in which the processof light absorbtion, charge separation and transmission happened in different parts.The charge separation in it is mainly realized by the charge getting and losing processof the dye and the redox reacton between I-and I-3. For the past few years, DSSC hasbeen intensively studied for its easy fabrication process,low cost and environmentalfriendliness. After twenty years of development,the energy conversion efficiency ofDSSC has already got to as high as12.3%under the simulated sunlight (standard AM1.5)[1]. With more research on DSSC and the improvement of its performance, it isexpected to be a credible alternative to the conventional silicon solar cell.As an essential constituent part of DSSC, counter electrode plays an importantrole in DSSC’s performance.Most high efficiency DSSCs that have been reported sofar are fabricated with counter electrode made of Pt, however, Pt is a rare elementwith high price, which restricts the extensive use of DSSC. Consequently, is a focusedissue for DSSCs’ development to design and prepare new kinds of counter electrodematerials with both high catalytic activity and low cost.The idea of preparing DSSC counter electrode made of Co-Pt alloy is proposedin this article. Cobalt,a low cost metal with some catalytic activity and fairly highconductivity is introduced into the DSSC, and form a nano alloy catalyst with Pt inthe DSSC,which significantly improves the conductivity of the electrode, and lowersits cost.The combination of the two kinds of metal also produces synergyeffect,offering more active sites for the catalytic reaction,which enhance the catalyticactivity of the counter electrode significantly.In this article,we mainly study on thecontents listed as follow,(1) Co-Pt alloy with different compositions were prepared by potentiostaticmethod, and their physical and electrochemical performance were studied detailed.The SEM result indicates that the counter electrode was Co-Pt alloy whose particlesize was about tens of nanometers, with uniform constituent grains and small channelslocally on the saface. The higest power conversion efficiency of the DSSC assembledwith the Co-Pt alloy was recorded as10.23%, which was much higher than6.52%of the DSSC based standard Pt counter electrode under the same conditions. The Co-Ptalloy electrode also showed good cycle performance. The influences of thedeposition potential, the concentration ratio of the solution on the morphologyand electrochemical performance of the Co-Pt alloy counter electrodes.(2) Co-Pt alloy was prepared by hydrothermal reduction method using NaBH4as a reducing agent. The physical properties of Co-Pt alloy were characterized bySEM and XRD. The results indicated that a metal alloy phase was formed. The Co-Ptalloy paticles presented cotton flocculent shape, which had fairly bigspecific surface area. After mixed with PVDF binder, the Co-Pt alloy was coated onthe FTO conducting glass by the scraper technology, then the Co-Pt alloy counterelectrode was got. By optimizing the proportion of the two metals in the solutions, theCo-Pt counter electrode with the best catalytic property was prepared, and the powerconversion efficiency of DSSC based the best Co-Pt counter electrode was achieved7.61%.