Spectroscopic ellipsometry characterization of vacuum-deposited organic films for the application in organic solar cells

► Variable angle spectroscopic ellipsometry is applied to the absorber material DCV6T. ► Use of interference enhanced substrates ensures uniqueness of the results. ► DCV6T exhibits high anisotropy with preferred lying orientation of the molecules. ► Anisotropy in the neat DCV6T layer is enhanced by post-annealing. ► Anisotropy is also present in mixed layers DCV6T:C60 but decreases with annealing.