X-ray analysis for solar films

About three years ago companies on the photovoltaics sectors approached Norbert Langhoff. His company, IfG Institute for Scientific Instruments GmbH, develops highly complex X-ray systems for analysing materials. “Elbrus XRF” is the name given to a system that analyses the film on PV modules.

The devices and methods developed by IfG gain completely new “insights”, particularly in the analysis of substances and structures. One of these methods analyses pigments to verify the genuineness of paintings in museums. Others are utilised in medical diagnostics and therapy, for instance in the pinpointed destruction of cancer cells.

The production of PV modules based on so called CIGS, a thin film technology, involves vapour depositing submicrometre films of molybdenum, copper, indium, gallium, and selenium on a glass substrate. A perfect, high quality film not only depends on its composition, but also on its precise thickness. The measuring system “Elbrus” developed by IfG examines the film thickness and composition and rectifies imprecisions during the production process itself.

This is made possible by X-ray fluorescence spectroscopy. X-ray optics focus a beam with a short wavelength of only a few nanometres on the material, in this case the film on the glass substrate. The beam impinging on the film liberates electrons from deeper atomic energy levels, and the vacancies are filled with electrons from higher energy levels. The difference in energy is emitted in the form of fluorescent radiation, which is analysed by ultra sensitive detectors in a measuring head. Because the radiation is characteristic of the emitting substance this method can determine both the constituent elements and their fractions.

The particular challenge is that the CIGS films are deposited not only on plane glass, but often on glass tubes as well. Langhoff’s company is as yet the only one in the world to master this analytical challenge.

Link: www.ifg-adlershof.de