Wet Chemistry Analysis

Wet chemical processes for the manufacture of solar cells entail precise process control if optimum process results are to be continuously guaranteed and chemicals consumption minimized. Fraunhofer ISE has accordingly developed various volumetric, chromatographic and spectroscopic methods for the automated determination of concentrations in chemical process baths. The information gained is used for further development of the processes.

The outcome of the process depends on the concentrations of the chemicals used. Over the course of the process, however, the chemicals are continuously consumed, while reaction products accumulate in the process solution. Optimal process control thus demands accurate knowledge of the concentrations present. Factors to be considered when selecting suitable analytical methods include not only sufficient precision but also investment and running costs and the potential for automation.
In our Photovoltaic Technology Evaluation Center (PV-TEC), various methods are tested with respect to their suitability for process control under industrial conditions. Titration and ion chromatography are used for automatic determination of bath components in acidic texturing baths. Alkaline texturing baths are analyzed with the assistance of acid-base titration combined with measurement of surface tension.
Particular attention is being paid to the application of near-infrared (NIR) spectroscopy. Development of an adapted calibration method has demonstrated that this very rapid and cost-effective measurement method is capable of determining concentration with high reliability and accuracy.

Methods and equipment:

The following equipment in particular is available for wet chemical analysis:

Inline:

• Near infrared (NIR) and UV-Vis spectroscopy
• Ion chromatography
• High pressure liquid chromatography (HPLC)
• Surface tension

Offline:

• Titration
• Ion chromatography
• Atomic absorption spectroscopy (AAS)
• Optical emission spectroscopy (ICP-OES)
• Voltammetry