Correlating facet orientation, defect-level density and dipole layer formation at the surface of polycrystalline CuInSe2 thin films
Elizabeth A, Conradi H, Sahoo SK, Kodalle T, Kaufmann CA, Kühne TD, Mirhosseini H, Abou-Ras D, Moenig H (2020)
Publication Type: Journal article
Publication year: 2020
Journal
Book Volume: 200
Pages Range: 463-470
DOI: 10.1016/j.actamat.2020.09.028
Abstract
Individual grains of chalcopyrite solar cell absorbers can facet in different crystallographic directions at their surfaces. To gain a deeper understanding of the junction formation in these devices, we correlate variations in the surface facet orientation with the defect electronic properties. We use a combined analytical approach based on scanning tunneling spectroscopy (STS), scanning electron microscopy, and electron back scatter diffraction (EBSD), where we perform these experiments on identical surface areas as small as 2 × 2 µm2 with a lateral resolution well below 50 nm. The topography of the absorber surfaces indicates two main morphological features: micro-faceted, long basalt-like columns and their short nano-faceted terminations. Our STS results reveal that the long columns exhibit spectral signatures typical for the presence of pronounced oxidation-induced surface dipoles in conjunction with an increased density of electronic defect levels. In contrast, the nano-faceted terminations of the basalt-like columns are largely passivated in terms of electronic defect levels within the band gap region. Corresponding crystallographic data based on EBSD experiments show that the surface of the basalt-like columns can be assigned to intrinsically polar facet orientations, while the passivated terminations are assigned to non-polar planes. Ab-initio calculations suggest that the polar surfaces are more prone to oxidation and resulting O-induced defects, in comparison to non-polar planes. Our results emphasize the correlation between morphology, surface facet orientations and surface electronic properties. Furthermore, this work aids in gaining a fundamental understanding of oxidation induced lateral inhomogeneities in view of the p-n junction formation in chalcopyrite thin-film solar cells.
Involved external institutions
Universität Paderborn
Germany (DE)
Helmholtz-Zentrum Berlin für Materialien und Energie (HZB)
Germany (DE)
Westfälische Wilhelms-Universität (WWU) Münster
Germany (DE)
Germany (DE)
Helmholtz-Zentrum Berlin für Materialien und Energie (HZB)
Germany (DE)
Westfälische Wilhelms-Universität (WWU) Münster
Germany (DE)
How to cite
APA:
Elizabeth, A., Conradi, H., Sahoo, S.K., Kodalle, T., Kaufmann, C.A., Kühne, T.D.,... Moenig, H. (2020). Correlating facet orientation, defect-level density and dipole layer formation at the surface of polycrystalline CuInSe2 thin films. Acta Materialia, 200, 463-470. https://doi.org/10.1016/j.actamat.2020.09.028
MLA:
Elizabeth, Amala, et al. "Correlating facet orientation, defect-level density and dipole layer formation at the surface of polycrystalline CuInSe2 thin films." Acta Materialia 200 (2020): 463-470.
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