Graphene-Perovskite Solar Cells Exceed 18% Efficiency: A Stability Study

Interface engineering is performed by the addition of graphene and related 2D materials (GRMs) into perovskite solar cells (PSCs), leading to improvements in the power conversion efficiency (PCE). By doping the mesoporous TiO2 layer with graphene flakes (mTiO(2)+G), produced by liquid-phase exfoliation of pristine graphite, and by inserting graphene oxide (GO) as an interlayer between the perovskite and hole-transport layers, using a two-step deposition procedure in air, we achieved a PCE of 18.2%. The obtained PCE value mainly results from improved charge-carrier injection/collection with respect to conventional PSCs. Although the addition of GRMs does not influence the shelf life, it is beneficial for the stability of PSCs under several aging conditions. In particular, mTiO(2)+G PSCs retain more than 88% of the initial PCE after 16h of prolonged 1sun illumination at the maximum power point. Moreover, when subjected to prolonged heating at 60 degrees C, the GO-based structures show enhanced stability with respect to mTiO(2)+G PSCs, as a result of thermally induced modification at the mTiO(2)+G/perovskite interface. The exploitation of GRMs in the form of dispersions and inks opens the way for scalable large-area production, advancing the possible commercialization of PSCs.