New Method for Bandgap Imaging in Photovoltaic Modules

New Method for Bandgap Imaging in Photovoltaic ModulesIn manufacturing, the method enables quality control and early detection of changes in the production process, and in research, the method enables detecting non-homogeneity and the possibility to optimize the processes of applying thin layers of semiconductors, which are an active part of solar cells.


Authors:
Matevž Bokalič, Marko Topič, Bart E. Pieters, Andreas Gerber, Uwe Rau


The research group at the Faculty of Electrical Engineering of the University of Ljubljana (Matevž Bokalič, Marko Topič), in cooperation with the Forschungszentrum Jülich Institute (Bart E. Pieters, Andreas Gerber, Uwe Rau), developed a unique method for absorber bandgap imaging in photovoltaic modules with variable stoichiometry. The method is based on the appearance of luminescence, where the optoelectronic element emits light under the effect of excitation. The light is captured in two or several different spectral regions, where different cameras with different spectral responses can be used. On the basis of the calibration relation and the ratio of captured images, the absorber bandgap is determined – EG (xy) – throughout the surface of the photovoltaic module. The advantage of the new method is an extremely fast determination of absorber bandgap across the surface of the photovoltaic module, which the existing method did not deliver. The speed and non-destructiveness of the method enable in-situ use in the industrial environment as well as in research. In the production context, it enables quality control and early detection of changes in the production process, whereas in research, it enables detecting non-homogeneity and provides the possibility of optimizing the processes of applying thin layers of semiconductors, which are an active part of solar cells.

The method’s results enable both an improved understanding of the operation as well as quality control of the production of PV modules, both of which are crucial for the development and production of even more efficient and affordable PV modules. The developed method is a global innovation in the characterization of photovoltaic modules, thus it is covered by German and European pending patent application. The engagement of the University of Ljubljana in the patent is 70%. 
 

Sources: 1. Bokalič M, Pieters BE, Gerber A, Rau U, Topič M. Bandgap imaging in Cu(In,Ga)Se2 photovoltaic modules by electroluminescence. Progress in Photovoltaics: Research and Applications, Feb 2017. (IF = 6.72)
2. Bokalič M, Pieters BE, Gerber A, Rau U, Topič M. Bandgap Fluctuations Observed by EL in various Cu(In,Ga)(Se,S)2 PV Modules. IEEE Journal of Photovoltaics, Accepted for publication, 2017. (IF = 3.71)
3. Bokalič M, Topič M, Gerber A, Pieters BE, Rau U. Method and device for the determination of a measure of band gaps at optoelectronic components. Pat. Pending: PCT/EP2016/080910, 2016