Coatings on industrial semi-finished and finished products help create specific properties such as protection from heat and reflections. The efficiency and performance of thin-film solar modules are especially reliant on mature coating technologies, since they require large-surface, homogenous coatings with electro-optical functions. The various properties of the layers, such as microstructure, roughness, light transmission and homogeneity, have a significant impact on the efficiency of these solar modules. To date, it has only been possible to define these properties in very small test pieces.

“Together with industrial users, we are developing an innovative measurement procedure that allows us to reliably analyze the layer properties of thin-film modules with areas of up to two square meters – on a large scale and with non-destructive testing. The measurement technology will be inline-compatible; in other words, it can be integrated into existing manufacturing processes,” says Prof. Ralph Gottschalg, Director of the Fraunhofer CSP.

In addition to existing measurement procedures, the researchers are also using new analysis methods such as hyperspectral processes; the spectrally resolved data allows conclusions to be drawn about sample characteristics such as layer thickness, refraction indices and absorption edges. In order to scale this up to large formats, a metrology platform is being developed along with a prototypical measuring device, which can be customized for use in a specific production environment. Data gained through the platform allows customers to achieve better process control, which positively impacts the efficiency of the modules.

Since different semi-finished products have different optical and electro-optical requirements when it comes to measuring certain layer properties, the research project considers flexible measurement concepts and measurement configurations: “In order to coordinate applications with the respective purpose and the target value to be determined, tests are performed on smaller substrates and semi-finished products, which are manufactured in cooperation with the product partners using typical process variations,” says Dr. Christian Hagendorf, Project Manager at the Fraunhofer CSP. In this process, LED lighting units allow for homogeneous and spectrally selective radiation, which guarantees lossless precision during the transfer from lab scale to industrial sizes.

The findings in the areas of material characterization, technology development and measurement technologies can also be transferred to projects in the coatings, glass and semiconductor industry; the measurement platform developed at the Fraunhofer CSP is available for these types of projects as well.

The research project has a duration of three years and is funded by the European Regional Development Fund (EFRE). Associated project partners are Calyxo GmbH, Solibro Hi-Tech GmbH, f|glass GmbH, Wavelabs GmbH, ACM coatings GmbH, point electronic GmbH, Dosatsu GmbH and engineering firm Rosonsky.