Organic light emitting diodes (OLEDs) are considered to be one of the most promising technical approaches for the production of diffuse, large area light sources. OLEDs are built-on layer sequences of organic, semiconductive molecules. This diode type is already in use for production of small displays and a fast development of this optical technology is expected in the next years.
Right now OLED reasearch is focussing on a development of new organic molecules as well as on the optimisation of the OLED layer sequence. It is therefore understood that a chemical characterisation of OLEDs is preferable for the clarification of the following analytical questions:
So far ToF-SIMS depth profiling could provide mainly elemental information on layer sequences. The invention of a new Ar cluster ion source for sample erosion offers now the possibility to gain detailed organic information from molecular layer sequences. As an example a depth profile of an OLED test strucure is presented in the given plot. In this depth profile all listed substances were detected by means of their molecular ions (e.g. NPD: C44H33N2+). Thus, this new approach of organic depth profiling makes it possible to analyse organic layer systems in detail and to address analytical problems which could not be solved wth ToF-SIMS so far.