Supplementary Material

The real and imaginary part of dielectric function, The extinction coefficient, The bandgap estimated from Tauc plot, The SEM scan and corresponding EDS analysis, XRD data, Time-dependent evolution of the normalized peak absorbance.

Fig. S1. (a) Experimental and fitted real and imaginary dielectric constant spectra, determined by spectroscopic ellipsometry (SE). (b) the extracted extinction coefficient (k) of CZOS thin film under the humidity test within the time period of 0–96 h.

Fig. S2. The bandgap estimated from the Tauc plot under (a) 80% RH, (b) temperature, (c) illumination, and (d) combined humidity–temperature. The bold linear segments show the fitting windows used for bandgap extraction.

Fig. S3. (a) SEM scan of CZOS thin film after 30 days under humidity test. (b) corresponding EDS analysis.

Fig. S4. SEM scans and corresponding EDS of CZOS film under temperature stress: (a) as-grown, (b) 450 °C, and (c) 600 °C.

Fig. S5. Room temperature XRD of CZOS stored in vacuum for 335 days.

Fig. S6. Time-dependent evolution of the normalized peak absorbance of CZOS film under (a) combined humidity-temperature, (b) temperature, (c) illumination.

Table S1. The fitting parameters of CZOS thin film extracted from SE. Phase 1 and 2 refer to sulfur-rich and oxide-rich phases, respectively.

Table S2. Summary of the CZOS thin films used in the different aging experiments, including the test condition, film thickness extracted via ellipsometry, and as-grown optical bandgap.

© H. Althubyani et al., Published by EDP Sciences, 2026