Sn Substitution by Ge: Strategies to Overcome the Open-Circuit Voltage Deficit of Kesterite Solar Cells

Choubrac L, Bär M, Kozina X, Felix R, Wilks RG, Brammertz G, Levcenko S, Arzel L, Barreau N, Harel S, Meuris M, Vermang B (2020)

Publication Type: Journal article

Publication year: 2020

Journal

ACS Applied Energy Materials American Chemical Society

Book Volume: 3

Pages Range: 5830-5839

Journal Issue: 6

DOI: 10.1021/acsaem.0c00763

Abstract

Current state-of-the-art Cu2ZnSn(S,Se)(4) kesterite solar cells are limited by low open-circuit voltages (V-OC). In order to evaluate to what extent the substitution of Sn by Ge is able to result in higher V oc values, this article focuses on Cu2ZnGeSe4 "CZGSe" devices. To reveal their full potential, different strategies are explored that, in particular, aim at the optimization of the CZGSe/buffer heterojunction. Here, employing hard X-ray photoelectron spectroscopy, it is evidenced that only a combination of different surface treatments is able to remove all detrimental secondary phases. Further improvements are achieved by establishing a solar cell heat treatment in air. A systematic study of the impact of different annealing temperatures and durations determines the best heat treatment parameters to be 60 min at 200 degrees C. Also, Zn(O,S,OH) as a more transparent alternative to the heavy-metal compound CdS buffer layer has been realized. Combining all of the strategies, solar cells with 8.5 and 7.5% total area efficiency have been prepared, which is a record for Sn-free kesterite solar cells and any kesterite solar cell with a Zn(O,S,OH) buffer, respectively. Beyond these records, this work clearly confirms the emerging trend that Ge-for-Sn substitution is a successful strategy to improve the V-OC of kesterite solar cells.

Authors with CRIS profile

Marcus Bär Professur für Röntgenspektroskopie (HIERN)

Involved external institutions

Hasselt University / Universiteit Hasselt BE Belgium (BE) Helmholtz-Zentrum Berlin für Materialien und Energie (HZB) DE Germany (DE) Université de Nantes FR France (FR)

How to cite

APA:

Choubrac, L., Bär, M., Kozina, X., Felix, R., Wilks, R.G., Brammertz, G.,... Vermang, B. (2020). Sn Substitution by Ge: Strategies to Overcome the Open-Circuit Voltage Deficit of Kesterite Solar Cells. ACS Applied Energy Materials, 3(6), 5830-5839. https://doi.org/10.1021/acsaem.0c00763

MLA:

Choubrac, Leo, et al. "Sn Substitution by Ge: Strategies to Overcome the Open-Circuit Voltage Deficit of Kesterite Solar Cells." ACS Applied Energy Materials 3.6 (2020): 5830-5839.

BibTeX: Download