Ellipsometric study of the optical transitions of PC60BM and PC70BM thin films

•We determine the optical properties of two fullerene derivatives using ellipsometry.•Multisample analysis is applied to verify the uniqueness of the model.•The energy position of the oscillators used are compared with ones present in the parent molecules.

Spectroscopic ellipsometry is used to determine the optical properties and to extract electronic transitions of PC60BM and PC70BM thin films in the UV-Visible range. By means of a sum of Gaussian oscillators, the imaginary parts of dielectric functions of both materials are modeled. The physical meaning of each model is checked by comparing the energy position of the oscillators with known optical transitions of the C60 and C70 molecules as revealed in literature by others techniques. It is shown that spectroscopic ellipsometry is a powerful technique to investigate the electronic structure of pi-conjugated molecules.

Graphical abstractDownload full-size image