Activation of CdTe-based thin films with zinc chloride and tetrachlorozincates

A series of CdTe thin film solar cells were prepared by applying aqueous solutions of ZnCl2 or tetrachlorozincates MnZnCl4 (M=Na or NH4 for n=2; M=Mg or Ca for n=1) as flux reagents in the activation process, instead of established but highly toxic CdCl2. The remaining process steps for the generati...

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Bibliographic Details
Published in:Thin solid films 2015-05, Vol.582, p.100-104
Main Authors: Drost, C., Siepchen, B., Krishnakumar, V., Späth, B., Kraft, C., Modes, T., Zywitzki, O.
Format: Article
Language:English
Subjects:
Activation
Aqueous solutions
Cadmium telluride
Cadmium tellurides
Dip coatings
Field emission
Photovoltaic cells
Solar cells
Thin film solar cells
Thin films
Zinc chloride
Zincate
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Summary:A series of CdTe thin film solar cells were prepared by applying aqueous solutions of ZnCl2 or tetrachlorozincates MnZnCl4 (M=Na or NH4 for n=2; M=Mg or Ca for n=1) as flux reagents in the activation process, instead of established but highly toxic CdCl2. The remaining process steps for the generation of solar cells have not been varied and activation-temperature and -duration were kept constant with 400°C/25min. The back contact comprised an etching step followed by deposition of ca. 150nm gold. In contrast to Na2ZnCl4 and (NH4)2ZnCl4, the application of ZnCl2 or CaZnCl4 in 30% concentration gave promising results with current–voltage and quantum efficiency cell-data well comparable to CdCl2 standard activated reference cells. The aqueous solutions were either applied manually by dip-coating or sponge roller procedure. Microstructural and interfacial investigations were performed with high resolution field emission scanning electron microscopy imaging on polished cross sections of ZnCl2- or CaZnCl4-derived devices using ion beam preparation techniques. Moreover, the measurement of the electron beam induced current was achieved, yielding a similar appearance for a CaZnCl4-activated substrate compared to referential CdCl2 samples. •ZnCl2 or CaZnCl4 can substitute toxic CdCl2 in the activation of CdTe.•Activation process parameters are similar to standard CdCl2 activation.•Well comparable current–voltage cell data is obtained for Zn-based activation.•Microstructure for Zn-based cells compares well with standard CdCl2-cells.
ISSN:0040-6090
1879-2731
DOI:10.1016/j.tsf.2014.09.001