Unveiling the reactivity of Cu(In_0.7Ga_0.3)Se₂ Absorbers Induced by High Relative Humidity and Illumination: Insights From Surface to Bulk.

Authors

Anna Gagliardi, Olivier Heintz, Anna Krystianiak, Thierry Conard, Derese Desta, Amelle Rebai, Negar Naghavi, Arnaud Etcheberry, Jean-François Guillemoles, Muriel Bouttemy, Solène Béchu

Published in

Small (Weinheim an der Bergstrasse, Germany). Pages e75147. Aug 17, 2026. Epub Aug 17, 2026.

Abstract

Since Cu(In_xGa_{1 - x})Se₂ (CIGS) absorbers are among the most efficient materials for photovoltaic energy conversion, it is crucial to understand their degradation mechanisms and the key factors driving them. To do so, we present aging studies up to 2000 h at 80% relative humidity and 20°C, first under illumination and then in the dark. Three complementary techniques are used to unveil the evolution of the absorber at different probing depths. Surface and subsurface chemical reactivities are investigated, respectively, thanks to XPS (x-ray Photoelectron Spectroscopy) and HaXPES (Hard x-ray Photoemission Spectroscopy) characterizations (probing from 3 up to 41 nm). In addition, EDS (Energy Dispersive Spectroscopy) measurements unveil the bulk chemical reactivity at 0.7 and 1.3 µm. The main result is a greater sensitivity of the absorber's surface when RH is combined with light rather than dark exposure, which triggers the CIGS network faster, leading to oxide phase growth, Se⁰ side phases appearance, and Na diffusion. This shows that the degradation is boosted in the presence of light. On the other hand, the CIGS bulk results intact around 1 µm under all the ambient conditions investigated.

PMID:
42605520
Bibliographic data and abstract were imported from PubMed on 17 Aug 2026.

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