The Study Of Carbon/Polymer Composite Counter Electrode For Dye-Sensitized Solar Cells

Dye sensitized solar cell (DSSC) is a kind of new-style P-N junctionphotovoltaic device, which is according to principle of photosynthesis. Itpossesses rich materials, low cost, simple fabrication process, and no pollutionto the environment, which make it has a relatively stronger competitiveness inthe large-scale production. So the study about DSSC has great practicalsignificance. At present, the key to study of DSSC are how to improve theefficiency of converting light to electricity and stability of DSSC. To prolongthe service life of the cells is another important thing.The counter electrode is one of the most important components in theDSSCs, which strongly affects the fill factor and light-to-electricity of cells.For the moment, platinum-loaded conducting glass has already been widelyused as the standard for DSSC counter electrodes, because of its bettercatalytic activity forI-/I-3in the electrolyte. However, its expensive priceand rareness greatly limits its use. Metal substrate is difficult to employ forliquid-type DSSCs because theI-/I-3redox species in the electrolyte arecorrosive for it. Carbon material with low cost, high catalytic activity, andbetter conducting activity is a promising candidate for the replacement ofplatinum. Carbon counter electrode for the dye-sensitized solar cells isinvestigated in this paper.(1) Carbon black with low cost, high catalytic activity embedded in mixtures of poly(ethylene oxide) and poly(vinylidene fluoride-hexafluoropropylene) to make carbon/polymer composites slurry, whichwas deposited on transparent conducting glass substrate by doctor-bladecoating for application in dye-sensitized solar cells (DSSCs) as counterelectrode materials. The morphologies of carbon films were characterizedby scanning electron microscopy (SEM, SU-70, Japan). Electrochemicalimpedance spectroscopy (EIS) measurements were performed by anelectrochemical workstation (CHI650D, USA), which also gave the cyclicvoltammograms and bulk resistance of CEs. Functional films characteristictester (DHFC, China) was used to test square resistance of CEs. KLA-Tencor Alpha-step (IQ3, USA) was used to measure the thickness of films.The bulk conductivity of CEs is calculated.(2) The photocurrent–voltage (I–V) curves of cells were obtained bya Keithley model2400digital source meter. The irradiation source was asolar simulator (Newport, USA) that gave an AM1.5G illumination on thesurface of the solar cells. The incident light intensity (100mW cm-2) wascalibrated with a standard Si solar cell. We investigated the influence forDSSC from the concentration of carbon slurry and the thickness of carbonfilm. The experiments indicate that the photovoltaic parameters of DSSCsare strongly dependent on the carbon concentrations in the slurry. Thedevice with carbon counter electrode whose mass ratio is1:1(mass ratio=carbon black mass: polymers mass), exhibited an overall energyconversion efficiency of4.62%, which was comparable to5.32%of thatwith platinum as a counter electrode under the same test condition.