The Energy Level Alignment at the Buffer/Cu(In,Ga)Se2 Thin-Film Solar Cell Interface for CdS and GaOx

Valenta D, Yetkin HA, Kodalle T, Bombsch J, Garcia-Diez R, Hartmann C, Ueda S, Félix R, Frisch J, Bodenstein-Dresler L, Wilks RG, Kaufmann CA, Bär M (2024)

Publication Type: Journal article

Publication year: 2024

Journal

Advanced Materials Interfaces WILEY-VCH Verlag GmbH & Co. KGaA

DOI: 10.1002/admi.202301110

Abstract

Sputter-deposited GaOx (i.e., oxygen-deficient gallium oxide) films are evaluated as a potential replacement for the standard CdS buffer layers in Cu(In,Ga)Se2 (CIGSe) based thin-film photovoltaics. The energy level alignment at the GaOx/CIGSe and CdS/CIGSe interfaces are compared by means of direct and inverse photoemission. For the GaOx/CIGSe a (0.04 ± 0.07) eV (i.e., a small spike-like) conduction band offset (CBO) and a (−3.21 ± 0.19) eV (i.e., a large cliff-like) valence band offset (VBO) are found, which suggests a nearly ideal charge-selective contact. The derived GaOx band gap of (4.80 ± 0.25) eV confirms its utility as a highly transparent buffer layer. However, the GaOx (with x derived to be 1.1 ± 0.1) exhibits considerable (presumably) defect-related occupied states above the valence band maximum. It is proposed that these states may increase charge carrier recombination and decrease open circuit voltage in respective devices; also explaining why solar cells with standard CdS buffer outperform devices with GaOx buffer, despite less ideal electronic interface properties (CBO: (−0.18 ± 0.07) eV, VBO: (−0.98 ± 0.15) eV) and the smaller CdS band gap of (2.35 ± 0.22) eV.

Authors with CRIS profile

Marcus Bär

Involved external institutions

Helmholtz-Zentrum Berlin für Materialien und Energie (HZB) DE Germany (DE) National Institute of Materials Science (NIMS) JP Japan (JP)

How to cite

APA:

Valenta, D., Yetkin, H.A., Kodalle, T., Bombsch, J., Garcia-Diez, R., Hartmann, C.,... Bär, M. (2024). The Energy Level Alignment at the Buffer/Cu(In,Ga)Se2 Thin-Film Solar Cell Interface for CdS and GaOx. Advanced Materials Interfaces. https://dx.doi.org/10.1002/admi.202301110

MLA:

Valenta, Donald, et al. "The Energy Level Alignment at the Buffer/Cu(In,Ga)Se2 Thin-Film Solar Cell Interface for CdS and GaOx." Advanced Materials Interfaces (2024).

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