Coating Thickness Measurement and Analysis                                

X-Ray Fluorescence Analysis to Control the Quality of Photovoltaic - Thin Layer Cells

The blue reflective silicon solar panels attract more and more attention on our rooftops. As an alternative to this kind of solar panel, researchers have recently developed thin layer solar cells which consist predominantly of the elements Copper (Cu), Indium (In), Gallium (Ga) and Selenium (Se) or CIGS.  Derived from the chemical elements Cu (In,Ga) Se2 they are also known as CIS-cells. The polycrystalline CIS-solar cells are hoped to be cheaper to both buy and produce.

Precise EDXRF-Analyser measures the characteristic of the CIS-solar cells

The thickness of the (CIGS) absorber layers and the In-Ga-Se-composition, are a closely guarded secret of the manufacturers because they influence, among other things the efficiency of the device (in the laboratory more than 18 % efficiency has been achieved). By varying the composition, the sensitive wavelength range of the CIGS-layer can be matched to the solar spectrum. For the highest efficiency the absorber layer proportions of In, Ga, Se have to be within tight tolerance limits.

That applies to the CIGS-Layer thickness, too. The energy dispersive X-Ray fluorescence analysis technique, used by Fischer X-RAYs, is ideal for the non-destructive and contact-free determination of the composition and coating thickness of the CIGS-thin layer. The software package WinFTM® not only measures the functionally important CIGS-layer but also the thin ZnO- and CdS-layer above, and if appropriate, the Mo-layer below.  In additon, the composition of the glass substrate can be measured.

Application in the measuring laboratory

It is desirable that instruments with semiconductor detectors are used because they provide better accuracies for the important compositions of In, Ga and Se. When measuring small objects, the Fischer X-RAY XAN®-DPP is the correct choice. When measuring large specimens it must be proved that the tight tolerances for In, Ga and Se are kept over the whole panel area. For this application (scanning of the surface) X-ray devices with a programmable XY-measurement stage are ideal, the Fischer XDV®-SD or the Fischer X-RAY XDAL®.

Measurement certainty

The repeatability for the measurement on CIS-layers is better than 0.01 µm for the determination of the layer thickness and for the measurements of the concentrations Cu, Ga, Se (XDV®-SD) at best within the range 0.03 % to 0.09 % with a measuring time of 100 sec.

Inline applications in the coating process

Customised measuring heads for the Fischer X-RAY CONTI 4000 DPP are available, which can be coupled to an evacuated process chamber. The measurements serve as process monitoring and process control.

Coating Thickness Measurement and Material Analysis Downloads

An overview of x-ray spectrometers for coating thickness measurement and materials analysis click here

WinFTM V6 software for coating thickness measurement and materials analysis click here

X-Ray spectrometer (XAN) for quantitative material analysis click here 

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