Surface and Film Characterization

© Fraunhofer CSP

Elektronenmikroskopbild einer verschmutzten Glasoberfläche mit Darstellung chlorhaltiger Salzverbindungen in grüner Farbe.

Photovoltaic modules have to withstand harsh environmental conditions during their service life. The chemical, electrical and mechanical properties of the module layer stack play a key role in this process. We offer high-resolution and highly sensitive layer analysis at all integration levels of PV modules. Module defects can then be traced back to the atomic level using transmission electron microscopy (TEM) after localization with electro-optical methods, which often provides the basis for understanding and eliminating the causes of defects. In addition, we are developing novel test methods for the evaluation of module degradation effects. For example, the in-house developed dust test chamber helps our customers to develop dust-repellent glass coatings. It makes it possible to realistically adjust the conditions under which dust "clings" to surface.

Services

  • Contamination and cleaning tests on glass surfaces
  • Defect diagnostics in thin-film PV: localization, target preparation and microstructure analysis
  • Elemental analysis in layer stacks: Quantitative surface and depth profile analyses with ToF-SIMS, XPS, TEM
  • Preparation (magnetron sputtering) and characterization of functional thin films
  • Voltage degradation tests and high-voltage leakage current tests

Examples

© Fraunhofer CSP

Electro-optical methods and REM/EBIC (a) help to localize defects and contaminations in thin-film solar cells. Target preparation methods permits the identification of defects buried in the layer structure (b) and to draw conclusions on process faults.

Layer diagnostics in thin-film PV

Defects and impurities in thin-film solar cells are located using electro-optical methods and REM/EBIC (a). Target preparation methods can be used to find buried defects in the layer structure (b), which allow conclusions to be drawn about defects in the process. Advanced elemental analytical methods such as ToF-SIMS, XPS, TEM/EDX help to classify different types of defects.

© Fraunhofer CSP

Atomically resolved structure of the CIGS film.

Stacking error in the atomic structure of CIGS layers

Specially developed preparation processes are used to produce artifact-free cross-sections of sensitive thin-film systems such as CIGS solar cells. These allow the high-resolution imaging of the atomic structure in a transmission electron microscope (TEM). The figure shows local material defects due to irregularities in the ordered crystal structure of the atoms.

© Fraunhofer CSP

REM, FIB, TEM & EDX characterization of dust-soiled glass in a test field in Qatar.

Anti-soiling evaluation of glass coatings

In regions with high levels of airborne dust (e. g. deserts, cities) the dust deposits on the glass surfaces of the PV modules result in significant yield losses. This process is also known as "soiling". Anti-soiling layers can be used to minimize the cleaning effort. Microstructural characterization is helpful for understanding and checking the function of these dust-repellent layers. Under real desert conditions, for example, cementation processes take place in which dust particles are literally "baked" onto the glass. The simulation of such contamination processes in the laboratory is carried out at the Fraunhofer CSP using a specially developed test stand.
 

© Fraunhofer CSP

With the PIDcon test device, potential-induced degradation (PID) can be detected at the solar cell level.

PID test equipment for unencapsulated solar cells

For the evaluation of unencapsulated solar cells and module encapsulation materials with regard to their susceptibility to potential-induced degradation (PID), an integrated test device was developed at the Fraunhofer CSP. The patented test procedure is commercially available as PID cell tester "PIDcon" from Freiberg Instruments. With PIDcon it is possible to carry out PID tests on solar cells within a few hours and without the complex use of expensive climate chambers.

Based on this know-how, a PID module test device is currently being developed in cooperation with Freiberg Instruments to market maturity for use in the open field. PIDcheck allows modules to be tested for quality even after they have been installed in the field and to make statements about the susceptibility of modules to the PID effect. With a duration of four to eight hours, the device takes considerably less time to use than previous methods.

 
Further information on www.pidcon.com