Dr. Elham Soltani from Imperial College London visited Nanopto group for two weeks within the framework of the European StableNextSol Cost Action. The topic of the research carried out was the characterization and understanding of organic photovoltaics based on donor polymers and non-fullerene acceptors. Blends and bilayers were characterized by means of ellipsometry and Raman Spectroscopy. Furthermore, Dr. Soltani actively participated in the group by giving a summary talk during the weekly group meeting on Thursday. This stay is part of a long-term collaboration between the groups of Dr. Mariano Campoy (Nanopto, ICMAB-CSIC) and Prof. Jenny Nelson (Imperial College).