p–n junction improvements of Cu2ZnSnS4/CdS monograin layer solar cells

•S, Sn–O and/or Sn–Br species are formed on the CZTS crystal's after Br-etching.•KCN etching remained oxides and bromides on the surface until CdS deposition.•The Br-etched devices exhibit a “crossover” between the dark and the light I–V curve. In this work we studied the influence of oxidative...

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Bibliographic Details
Published in:Applied surface science 2015-12, Vol.357, p.795-798
Main Authors: Kauk-Kuusik, M., Timmo, K., Danilson, M., Altosaar, M., Grossberg, M., Ernits, K.
Format: Article
Language:English
Subjects:
Bromine
Cu2ZnSnS4
CZT
Deposition
Etching
P-n junctions
Photovoltaic cells
Solar cells
Sulfur
Sulfur oxidation
Surface treatment
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Summary:•S, Sn–O and/or Sn–Br species are formed on the CZTS crystal's after Br-etching.•KCN etching remained oxides and bromides on the surface until CdS deposition.•The Br-etched devices exhibit a “crossover” between the dark and the light I–V curve. In this work we studied the influence of oxidative etching of CZTS monograin surface to the performance of CZTS monograin layer solar cells. The chemistry of CZTS monograin powder surfaces submitted to bromine in methanol and KCN aqueous solutions was investigated by X-ray photoelectron spectroscopy. After bromine etching, elemental sulfur, Sn–O and/or Sn–Br species are formed on the CZTS crystal surface. Sulfur is completely removed by subsequent KCN etching, but oxides and bromides remained on the surface until CdS deposition. These species dissolve in alkaline solution and influence properties of CdS. The conversion efficiency of solar cells improved after the chemical etching prior to CdS deposition and the effect can be attributed to the change of the absorber material crystals surface composition and properties suitable for the effective p–n junction formation. The best CZTS monograin layer solar cell showed conversation efficiency of 7.04% (active area 9.38%).
ISSN:0169-4332
1873-5584
DOI:10.1016/j.apsusc.2015.09.094