Three-dimensional (3D) perovskite materials display remarkable potential in photovoltaics owing to their superior solar-to-electric power conversion efficiency, with current efforts focused on improving stability. Two-dimensional (2D) perovskite analogues feature greater stability toward environmental factors, such as moisture, owing to a hydrophobic organic cation that acts as a spacer between the inorganic layers, which offers a significant advantage over their comparatively less stable 3D analogues. Here, we demonstrate the first example of a formamidinium (FA) containing Dion Jacobson 2D perovskite material characterized by the BFA(n-1)Pb(n)I(3n+1) formulation through employing a novel bifunctional organic spacer (B), namely 1,4-phenyl-enedimethanammonium (PDMA). We achieve remarkable efficiencies exceeding 7% for (PDMA)-FA(2)Pb(3)I(10) based 2D perovskite solar cells resisting degradation when exposed to humid ambient air, which opens up new avenues in the design of stable perovskite materials.