Resolving multiple layer thicknesses and birefringence in thin films with an optical in-line Roll-to-Roll characterization setup
Optical techniques provide a fast and flexible path to material inspection. In particular, the investigation of key metrics during material production can help obtain the optimal parameters to achieve desired material functionality as well as to ensure product quality. Here we present an optical imaging setup designed for fast material inspection in a roll-to-roll deposition environment. The method allows for robust simultaneous determination of thickness in the range from 0.3 to 110 micrometers of multiple layers of transparent or semi-transparent materials in the form of a free film or a film deposited on a thicker transparent substrate. The PEDOT and ZnO materials chosen for this proof of concept are relevant for the fabrication of organic solar cells. Additionally, the method may be used to characterize birefringence.