The Effects of Spin-Coating Rate on Surface Roughness, Thickness, and Electrochemical Properties of a Pt Polymer Counter Electrode

In a dye-sensitized solar cell (DSSC) the CE is responsible for the collection of electrons from the external circuit and the electrocatalysis reaction of the electrolyte. This paper reports the effect of spin-coating rate on the surface roughness, film thickness, and electrochemical properties of a Pt polymer counter electrode (CE). In this work, the spin-coating rate has been investigated in the range 1000-6000 rpm and the results indicate that low spin-coating speeds produce the thickest films with the smoothest surfaces, while high spin speeds produce thinner films with higher surface roughness. The thickness of the film decreased from 7.03 μm at 1000 rpm to 1.30 μm at 6000 rpm. Results also indicate a decrease in electrocatalysis properties and conductivity with the increase in film spin-coat rate. The resistance at the CE/electrolyte interface decreased from 9.3 Ω at 1000 rpm to 14.8 Ω at 6000 rpm. The spin-coating rate also affects the light transmittance of the CE and photovoltaic characteristics of the DSSC, such as current density and overall cell conversion efficiency. This study demonstrates a method to develop cost-effective counter electrodes for application in bifacial solar cells.