Polymeric solar cells are a promising alternative for producing clean and renewable energy due to the possibility of fabricating them onto large areas of lightweight, flexible substrates by solution processing at low cost. In this context, oligothiophenes and polythiophenes are attracting increasing interest because they offer a range of promising properties. The conductivity of the materials is increased by doping with an electron acceptor and iodine is commonly used for this purpose. The properties crucially depend on the doping level. The aim of this proposal is to test whether VESUVIO can quantify both the amount of iodine present and the sulfur:iodine ratio in polythiophene. We will measure both a doped polythiophene and a compound of fixed and known stoichiometry, 2,5-diiodothiophene.