Impurity Analysis in Wet Chemical Baths in PV Processes

The monitoring of chemical solutions is an important factor for quality control in industrial high efficiency cell processing. In the solar cell industry, the possible contamination of wet chemical baths for texturing and cleaning with trace impurities has not yet been studied intensively. Questions concerning the desired bath purity or the maximum impurity load of the cleaning bath can only be answered empirically. In this paper the acidic texture bath is monitored by impurity analysis with inductively coupled plasma optical emission spectrometry (ICP OES) during the etching of upgraded metallurgical grade (umg)-mc-silicon. A further researched point is the influence of iron on the texture behaviour in the acidic texture bath and the consequence on the silicon surface contamination degree. The texture behaviour is investigated with scanning electron microscopy (SEM), the surface concentration was analysed with droplet collection/atomic absorption spectrometry (DC/AAS).