Investigation Of Counter Electrode Material For Dye-sensitized Solar Cells

Dye-sensitized solar cell （abbreviation: DSSC） is kind of device based on moleculeconstituents that can converse light to energy. Since the first report in1991by professorGr tzel, DSSC has become one of the most popular topics in the world for its facilefabrication and low cost. In general, DSSC consists of three main parts: a dye-sensitizedphotoanode, electrolyte containing a redox couple, and a counter electrode which can catalysethe regeneration of the redox couple. Counter electrode is of great importance to the wholecirculation of the DSSC, so investigation of counter electrode is one of the important researchfields of DSSC.In this paper, we fabricated a polyoxometalate modified Pt by electrochemicaldeposition method in which α-K₃H₄[SiW₉Al₃（H₂O）₃O₃₇·7H₂O andpoly（diallyldimethylammonium chloride）（denoted as PDDA）. The catalytic ability ofdifferent layer POM-modified counter electrode was also detected by ElectrochemicalImpendence Spectrum （denoted as EIS）. The EIS results showed that the series resistance ofthe POM-modified Pt counter electrodes was lower than bare Pt counter electrode, thecharge transfer resistant of different layer modified Pt counter electrodes is rising from1to3-layer modified counter electrode and then descending from3to5-layermodified counterelectrode, however charge transfer resistant of all of the POM-modified counter electrodewas lower than bare Pt counter electrode, thus POM-modified counter electrode possessedbetter catalytic ability than bare Pt electrode. Cyclic voltammetry （CV） method was alsoused to verify the EIS result, we calculated the peak separation of POM-modified counterelectrodes from the CV spectrum, and the3-layer modified counter electrode was lower thanthe bare Pt electrode, the results showed that POM-modified counter electrode possessedbetter catalytic ability than bare Pt electrode. Atomic microscopy images of POM-modifiedelectrode and bare Pt electrode were also detected, the surface of the POM-modifiedelectrode become smoother than Pt electrode, and some big nanoparticles were formed onthe surface of the electrode after modified by POM. The energy conversion of the cell with3-layer POM-modified counter electrode increased by1%, however the fill factor ofdecreased negligible, we investigate the result by open-circuit voltage decay method, andfound that the lifetime of the electrons in photoanode decreased. Incident photon conversionefficiency （denoted as IPCE） was also carried out, the light to energy conversion efficiencyof POM-modified electrode was higher than bare Pt between400to800nm.Cu₂O electrodes were fabricated by synthesizing Cu₂O micrometer particles onFluorine-doped tin oxide （FTO） glass substrates by one-step polyol synthesis method in the mixture solution of ethylene glycol and water solution. SEM figures showed that most of theas-prepared Cu₂O micrometer particles were of truncated cubic structure and very fewparticles were of26-facet polyhedral structure. XRD results showed that the micrometerparticles are abundant in （100） facets. And the catalytic ability of the as-prepared Cu₂Oelectrodes for the regeneration of I-was also detected by cyclic voltammograms,electrochemistry impendence spectroscopy and Tafel polarization methods. The resultsindicated that the as-prepared Cu₂O electrodes show better catalytic ability than CuO/Cu₂Oelectrodes could be a candidate for counter electrodes in dye-sensitized solar cells.