Johannes Hepp
Bavarian Center for Applied Energy Research, Germany
Title: Automatized optical quality assessment of photovoltaic modules
Biography
Biography: Johannes Hepp
Abstract
Optical measurement techniques open the door to a wide variety of quality inspection tools. However, the number of customizable settings, like e.g. excitation sources or optical fi lters, is immense. For the quality inspection of thin film photovoltaics, we developed a Matlab based analysis tool in order to investigate as many parameters-potentially obtained by diff erent metrology methods-as possible, in a fast and reproducible way. Th is tool automatically executes procedures like peak wavelength detection of luminescence spectra (an indicator for material composition), hot spot detection in IR images (an indicator for recombination losses) and many mathematical combinations of multiple images taken under varying conditions. One application of this approach was to separate the eff ects of material composition from the infl uence of the defects on the performance of a photovoltaic module. Th e combination of these two performance indicators showed a good correlation to
the open circuit voltage of the device, proving the relevance of this analysis approach. Furthermore, the tool was capable of capturing further refi nements following from hardware improvements like the combination of images taken with special IR fi lters. Th is allowed us to combine the benefi ts of spectral and spatial resolution, which could be used in order to selectively identify certain chemical substances and their distribution in the sample of interest. Th e soft ware applies the scripted processing tasks successively on all samples of a measurement series within minutes, thus enabling high throughput inline measurements. Th e implemented graphical user interface (GUI) allows for a fl exible and user defi nable handling.