Publication date: 17th February 2025
The effect of different barrier foils on the stability of methylammonium-formamidinium-cesium PSC was studied in damp heat induced aging over 2000 hours, at ISOS-D-3 aging test conditions. The devices were purposedly encapsulated between the flexible barrier foils, on top of the PSC silver contacts, and a glass slide. Electrical and spectroscopic characterization were performed at time intervals. The absorption spectra of only one group of PSC show a rapid decrease of the absorbance at 550 nm, due to perovskite chemical degradation to byproducts. All the PSC of the other groups show negligible changes in their absorption spectra, mainly after 1600h, showing little to none perovskite degradation, with no band gap variation, and still retain high PCE after 2000 h. The results were correlated with the films’ water vapour transmission rates: a fast chemical degradation occurs for the perovskite exposed to damp heat with the only protection of a barrier film having a 0.013 g/m2 24h WVTR value, which leads to cell degradation resulting from moisture exposure. The perovskite active layer remains largely intact when the WVTR is ≤0.002 g/m2 24h. This suggests that the observed PCE decrease is mainly associated with the metal-perovskite-encapsulant contact interface. Moreover, the strong correlation between PCE and Jsc mplies that the overall degradation is chiefly driven by a loss in charge carrier transport efficiency within the device.
The project has received funding from the European Union’s Horizon 2020 research and innovation programme. Funding reference: 101122283