Rb Diffusion and Oxide Removal at the RbF-Treated Ga2O3/Cu(In,Ga)Se2 Interface in Thin-Film Solar Cells

Elizaveta Pyatenko; Dirk Hauschild; Vladyslav Mikhnych; Raju Edla; Ralph Steininger; Dimitrios Hariskos; Wolfram Witte; Michael Powalla; Clemens Heske; Lothar Weinhardt

doi:10.1021/acsami.3c11165

Rb Diffusion and Oxide Removal at the RbF-Treated Ga₂O₃/Cu(In,Ga)Se₂ Interface in Thin-Film Solar Cells

ACS Appl Mater Interfaces. 2023 Nov 1;15(45):53113-53121. doi: 10.1021/acsami.3c11165. Online ahead of print.

Authors

Elizaveta Pyatenko^{1

2}, Dirk Hauschild^{2

3

4}, Vladyslav Mikhnych², Raju Edla², Ralph Steininger², Dimitrios Hariskos⁵, Wolfram Witte⁵, Michael Powalla⁵, Clemens Heske^{2

3

4}, Lothar Weinhardt^{2

3

4}

Affiliations

¹ Laboratory for Applications of Synchrotron Radiation (LAS), Karlsruhe Institute of Technology (KIT), Kaiserstraße 12, Karlsruhe 76131, Germany.
² Institute for Photon Science and Synchrotron Radiation (IPS), Karlsruhe Institute of Technology (KIT), Hermann-v.-Helmholtz-Platz 1, Eggenstein-Leopoldshafen 76344, Germany.
³ Institute for Chemical Technology and Polymer Chemistry (ITCP), Karlsruhe Institute of Technology (KIT), Engesserstraße 18/20, Karlsruhe 76128, Germany.
⁴ Department of Chemistry and Biochemistry, University of Nevada, Las Vegas (UNLV), 4505 Maryland Parkway, Las Vegas, Nevada 89154-4003, United States.
⁵ Zentrum für Sonnenenergie- und Wasserstoff-Forschung Baden-Württemberg (ZSW), Meitnerstraße 1, Stuttgart 70563, Germany.

PMID: 37913778
PMCID: PMC10659031 (available on 2024-11-01)
DOI: 10.1021/acsami.3c11165

Abstract

We report on the chemical structure of Cu(In,Ga)Se₂ (CIGSe) thin-film solar cell absorber surfaces and their interface with a sputter-deposited Ga₂O₃ buffer. The CIGSe samples were exposed to a RbF postdeposition treatment and an ammonia-based rinsing step, as used in corresponding thin-film solar cells. For a detailed chemical analysis of the impact of these treatments, we employed laboratory-based X-ray photoelectron spectroscopy, X-ray-excited Auger electron spectroscopy, and synchrotron-based hard X-ray photoelectron spectroscopy. On the RbF-treated surface, we find both Rb and F, which are then partly (Rb) and completely (F) removed by the rinse. The rinse also removes Ga-F, Ga-O, and In-O surface bonds and reduces the Ga/(Ga + In) ratio at the CIGSe absorber surface. After Ga₂O₃ deposition, we identify the formation of In oxides and the diffusion of Rb and small amounts of F into/onto the Ga₂O₃ buffer layer but no indication of the formation of hydroxides.

Keywords: Cu(In,Ga)Se2 thin-film solar cells; HAXPES; RbF postdeposition treatment; ammonia-based rinse; chemical structure; gallium oxide buffer layer; photoelectron spectroscopy; surface oxides.