Further strengthen by the recent achievement of 14 % certified PCE using perovskite/HTM combination^[1], the credibility of DSC for day-to-day utilization has never been as unequivocal as today. Beside such a record efficiency, establishing once again its reliable place in the photovoltaic panorama, to see it a light of day successfully introduced into the market, this last phase will now depend on how to make it more stable while preserving low-cost and sufficient PCE. Towards such objectives, two approaches are actually opposed: introduction of new materials by somehow playing at the naval battle vs. understanding the high complexity of the different chemical/electrochemical interactions between the DSC components, especially under temperature and/or light stresses. By simply looking at the actual scientific production in the domain, this top-down approach is much marginalized.

For long time, dye and sealant was culprit to account for the lack of stability. For instance, it is often answered that if the electrolyte leaks at a sudden moment it is because of poor sealing or if the performance is dropping upon ageing, it stems from the dye stability. Our principal research is actually focused on better understanding the chemical/electrochemical reactions which can take place in the cell upon ageing according to IEC61646 protocol. The objectives are to gather different experimental data to proposein fine a realistic mechanism accounting for the performance failure at elevated temperatures, to bring a beginning of an answer to the frequent speculations raised in the literature such as on the origin of iodine consumption or on why electrolyte leaks swiftly > 60°C whereas MPN boiling point is ca. 165°C.

Against the general preconceived idea, we will highlight during this presentation that one of the most stable DSC constituent, TiO₂, plays in reality a significant role on the electrolyte degradation^[2]. Indeed, based on the combination between a set of complementary techniques from gas / liquid chromatography, spectroscopic tools to transmission electron microscopy, we have highlighted (i) the formation of highly volatile compounds including gas evolution driven by the temperature and (ii) we revealed for the first time the growth of a conformal solid electrolyte interphase (SEI) layer wrapping not only TiO₂ but also the Pt catalyst at the counter-electrode. The chemical composition of this SEI will be described and the collateral implication of this SEI formation on both the electrolyte composition and device operation will be discussed on the basis of electrochemical impedance spectroscopy