Preparation and characterization of low platinum loaded Pt:SnO2 electrocatalytic films for screen printed dye solar cell counter electrode
A series of low platinum loaded Pt:SnO2 electrocatalysts for dye-sensitized solar cells were prepared by the hydrogen reduction method at 120 °C. As prepared and annealed at 630 °C samples containing 1.2%, 2% and 3% platinum loaded antimony doped tin dioxide catalytic powders were characterized. The structure and particle sizes are studied by means of high resolution transmission electron microscopy and X-ray diffraction measurement. The metallic state of platinum nanoparticles was observed by X-ray photoelectron spectroscopy. For the paste preparation, differently loaded Pt:SnO2 powders were each mixed with the ethylcellulose/terpineol printing media. In order to produce symmetrical Pt/Electrolyte/Pt cells for the electrochemical study the pastes were applied onto transparent conductive oxide coated glass by screen printing technology. The charge transfer resistance of these electrodes to the iodide/triiodide redox system in different electrolytes after the thermal sealing of the cells at 630 °C was investigated by electrochemical impedance spectroscopy, which showed that catalytic performance can be improved by homogenous deposition of catalyst on substrate. The surface morphology of the printed catalytic stripes was imaged by field emission scanning electron microscopy and atomic force microscopy.