Grain boundary passivation as an optimal strategy for perovskite solar cells with improved stability

High performance perovskite solar cells have been obtained using a variety of perovskite compositions. Here, we investigate the stability of different perovskite compositions that can yield efficient solar cells under exposure to different stressors: illumination (with oxygen or humidity) and elevated temperature. The sensitivity of the perovskite to different stress factors was strongly dependent on its composition, and stability-composition-efficiency relationships were complex. Nevertheless, MA-free perovskite clearly exhibits superior thermal stability and stability under illumination in oxygen, but it shows sensitivity to moisture. We then investigate the effect of common strategies for stability improvement, namely additives for defect passivation, hydrophobic additives, and cross-linking additives, on the stability of MA-free perovskite and achieved significant enhancement of stability with cross-linking additives. As cross-linking additives can hinder both ion migration under illumination and moisture ingress into the perovskite, they can facilitate superior stability compared to simple hydrophobicity enhancement. While all the additives resulted in similar efficiencies (∼22%), cross-linking additives resulted in an ∼1.7 times increase in T₈₀ compared to control devices during open circuit stability tests in ambient air with 70% relative humidity.