Effect of Na presence during CuInSe2 growth on stacking fault annihilation and electronic properties

While presence of Na is essential for the performance of high-efficiency Cu(In,Ga)Se2 thin film solar cells, the reasons why addition of Na by post-deposition treatment is superior to pre-deposition Na supply—particularly at low growth temperatures—are not yet fully understood. Here, we show by X-ra...

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Bibliographic Details
Published in:Applied physics letters 2015-10, Vol.107 (15)
Main Authors: Stange, H., Brunken, S., Hempel, H., Rodriguez-Alvarez, H., Schäfer, N., Greiner, D., Scheu, A., Lauche, J., Kaufmann, C. A., Unold, T., Abou-Ras, D., Mainz, R.
Format: Article
Language:English
Subjects:
Applied physics
Copper indium gallium selenides
Copper indium selenides
Current carriers
Deposition
Photovoltaic cells
Solar cells
Stacking faults
Thin films
X-ray diffraction
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Summary:While presence of Na is essential for the performance of high-efficiency Cu(In,Ga)Se2 thin film solar cells, the reasons why addition of Na by post-deposition treatment is superior to pre-deposition Na supply—particularly at low growth temperatures—are not yet fully understood. Here, we show by X-ray diffraction and electron microscopy that Na impedes annihilation of stacking faults during the Cu-poor/Cu-rich transition of low temperature 3-stage co-evaporation and prevents Cu homogeneity on a microscopic level. Lower charge carrier mobilities are found by optical pump terahertz probe spectroscopy for samples with remaining high stacking fault density, indicating a detrimental effect on electronic properties if Na is present during growth.
ISSN:0003-6951
1077-3118
DOI:10.1063/1.4933305