Polymer solar cells (PSCs) open up new perspectives in the solar cell market. The morphology of the active layer of PSCs plays a crucial role on the corresponding devices efficiency and different strategies have been developed for controlling it. The use of solvent additives, such as 1,8-diiodooctane (DIO), in addition to the primary host solvent has gained particular importance in recent years being very effective at improving the morphologies and PCEs of PSCs using some of the most recent high efficiency polymers. The neutron reflectivity (NR) in the current beam time application will be used to probe the vertical composition profiles of the active layers processed from several different pure solvents and solvents containing the additive DIO in different concentrations. The main goal is to elucidate how the DIO improves the morphologies and PCEs of the corresponding devices.
