Revealing the origin of the beneficial effect of cesium in highly efficient Cu(In,Ga)Se2 solar cells

Schoeppe P, Schoenherr S, Chugh M, Mirhosseini H, Jackson P, Wuerz R, Ritzer M, Johannes A, Martinez-Criado G, Wisniewski W, Schwarz T, Plass CT, Hafermann M, Kühne TD, Schnohr CS, Ronning C (2020)

Publication Type: Journal article

Publication year: 2020

Journal

Nano Energy Elsevier

Book Volume: 71

Article Number: 104622

DOI: 10.1016/j.nanoen.2020.104622

Abstract

The record conversion efficiency of thin-film solar cells based on Cu(In,Ga)Se2 (CIGS) absorbers has exceeded 23%. Such a high performance is currently only attainable by the incorporation of heavy alkali metals like Cs into the absorber through an alkali fluoride post-deposition treatment (PDT). As the effect of the incorporated heavy alkali metals is under discussion, we investigated the local composition and microstructure of high efficiency CIGS solar cells via various high-resolution techniques in a combinatory approach. An accumulation of Cs is clearly detected at the p-n junction along with variations in the local CIGS composition, showing the formation of a beneficial secondary phase with a laterally inhomogeneous distribution. Additionally, Cs accumulations were detected at grain boundaries with a random misorientation of the adjacent grains where a reduced Cu concentration and increased In and Se concentrations are detected. No accumulation was found at Σ3 twin boundaries as well as the grain interior. These experimental findings are in excellent agreement with complementary ab-initio calculations, demonstrating that the grain boundaries are passivated by the presence of Cs. Further, it is unlikely that Cs with its large ionic radius is incorporated into the CIGS grains where it would cause detrimental defects.

Involved external institutions

Friedrich-Schiller-Universität Jena DE Germany (DE) Universität Paderborn DE Germany (DE) Zentrum für Sonnenenergie- und Wasserstoff-Forschung (ZSW) DE Germany (DE) European Synchrotron Radiation Facility (ESRF) FR France (FR) Max-Planck-Institut für Eisenforschung GmbH (MPIE) / Max Planck Institute for Iron Research DE Germany (DE)

How to cite

APA:

Schoeppe, P., Schoenherr, S., Chugh, M., Mirhosseini, H., Jackson, P., Wuerz, R.,... Ronning, C. (2020). Revealing the origin of the beneficial effect of cesium in highly efficient Cu(In,Ga)Se2 solar cells. Nano Energy, 71. https://doi.org/10.1016/j.nanoen.2020.104622

MLA:

Schoeppe, Philipp, et al. "Revealing the origin of the beneficial effect of cesium in highly efficient Cu(In,Ga)Se2 solar cells." Nano Energy 71 (2020).

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