Spectroscopic ellipsometry is a powerful technique to characterize the thickness and optical constants of encapsulated OLED devices.

For the case of non-transparent encapsulation thecombination of ellipsometric measurements via the glass substrate and the powerful modelling features of DeltaPsi2 software make it possible to analyze “this reverse sample”.

Ellipsometric investigation of a 1-month aging process for an α-NPD film show a significant decrease of the refractive index, suggesting a decrease in the material density.