Ion beam studies of porphyrin adsorption on and leaching of soda lime glass

Abstract

Porphyrin organic dye layers on oxidic surfaces may play a key role in the light absorption and charge separation of organic solar cells. We report a study of the adsorption characteristics of positively charged porphyrins from an aqueous solution onto soda lime glass. Advanced surface analytical techniques (RBS, ERD and XPS) have been employed to study the layer growth of the porphyrins, in order to supplement the optical measurements of the layers. A linear growth of the amount of absorbed material is found. Leaching of the material by the carbonated solution appears to result in an increasing surface area available for deposition of porphyrins in the porous top layer of the glass. The ERD measurements indicate a surplus of hydrogen in the layer, which suggest the presence of H 2O in the porous glass layer. It is shown that the MeV ion beam techniques, which are not routinely applied in studies of organic thin films, can give meaningful results if one is aware of possible ion beam damage. The coverages found with these techniques are in good agreement with coverages determined with optical measurements. They have the additional benefit of depth profiling of these layers and determining the leaching of the glass.