Recently, organo-metal hybrid perovskite materials have attracted tremendous attention. This is due to their promising features such as solution processability, high crystallinity, direct and tunable band-gaps, and high hole/electron transport ability. In the photovoltaic field, perovskite solar cells thus represent a new paradigm, which has the potential to overcome the performance limits of current technologies and achieve low cost and high versatility. Nevertheless, this technology is known to be sensitive to the environmental factors. Consequently, presented work focuses on phenomena regulating both the reliability and efficiency of these solar cells.

First of all, the following optimized double-cation and double-anion perovskite formulation will be presented: FA_0.95Cs_0.05Pb(I_0.83Br_0.17)₃. In order to validate the enhanced performances and stability of this alternative perovskite, a device architecture compatible with both low temperature processes and semi-transparent devices for tandem cells development is here developed. The use of SnO₂ seems appropriate as electron transport layer (ETL) due to its higher electron mobility, charge-collection, UV stability and transmittance than traditional TiO₂. Regarding the hole transporting layer (HTL), the poly [bis (4-phenyl) (2,4,6-trimethylphenyl) amine] polymer possesses adequate energy levels, can act as a barrier to the penetration of moisture into the perovskite layer and is known to prevent the gold diffusion occurring with temperature from the electrode to the perovskite. Nevertheless, in order to maximize our perovskite initial performances, the addition of dopants (LiTFSI+ tBP) turned out mandatory.

In a second step, the impact of the doped HTL on the entire device stability will be exposed. Thanks to an optimized characterization set composed of X-ray diffraction, UV-visible absorption, photoluminescence, power conversion and external quantum efficiencies, the degradation behaviour of the presented perovskite has been draft. The tert-butylpyridine (tBP) constituent was evidenced to have a negative impact on the perovskite material stability by rapid production of three degradation phases. As represented in the below scheme in 85°C/dark/N₂ ageing conditions, the perovskite occurring degradation mechanism was found to be significantly lowered in the presence of gold electrode, leading us to hypothesize an interaction of pyridine with gold surface via the formation of a complex. Indeed, corresponding devices aged at 85°C without gold lose 72% of photovoltaic efficiency after 500 h against 28% when aged with gold.