Characterization of thin film solar cell layers by x-ray based spectroscopy

Synchrotron radiation can be used for various purposes. As it is a tunable X-ray source, it offers high brilliance light which can be provided polarized and in short pulses, new applications and measurement techniques where developed with its discovery. A short overview about the history and properties of synchrotron radiation will be given in this lecture

Photo electron spectroscopy (PES), also known as x-ray photo electron spectroscopy (XPS), is a powerful surface sensitive method that is based on the emission of electrons from the sample surface due to irradiation by x-ray light. The analysis of these electrons yields information on the elemental composition of the sample surface, and the chemical environment of each element. Examples will be given for the application of XPS for the characterization of thin film solar cell components

Photo electron spectroscopy using UV light for excitation (UPS) can be utilized to examine the weakly bound electrons (valence electrons) in a sample. Since these electrons are responsible for the chemical bonds in a compound, their analysis yields important information on the chemistry of a sample. In a semiconductor, the distance between the valence band and the Fermi level can be measured using UPS. Together with the value of the band gap, this information is used to determine the band line-up in a semiconductor device like a solar cell