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- Conflict of Interest
- In relation to this article, we declare that there is no conflict of interest.
- Publication history
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Received November 10, 2025
Revised November 10, 2025
Accepted November 21, 2025
Available online April 25, 2026
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This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/bync/3.0) which permits
unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
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Effects of Copper Stoichiometry on Cu(In, Ga)(S, Se)2 Thin-Film Solar Cells
https://doi.org/10.1007/s11814-025-00612-z
Abstract
Copper stoichiometry governs the structural, electronic, and photovoltaic properties of Cu(In, Ga)(S, Se)2 absorbers. This
review summarizes the effects of the Cu/(In +Ga) ratio on phase stability, defect thermodynamics, and band-edge modulation,
and discusses how Cu control contributes to device performance. Under Cu-rich conditions, transient Cu2-x(Se, S)
phases enhance grain growth but may cause metallic residues, while Cu-deficient compositions stabilize ordered vacancy
compounds that improve p-type conductivity and interface alignment. At the electronic level, reduced Cu content weakens
Cu-3d and (S, Se)-p coupling, lowering the valence band and widening the band gap by ~0.15–0.23 eV. An empirical Cudependent
extension of the conventional band gap relation is presented to describe this effect. The optimum Cu/(In +Ga)
range (0.85~0.95) ensures phase stability and minimal defect density, providing a basis for performance enhancement
through composition and depth-controlled Cu grading.
