Role of a hydrophobic scaffold in controlling the crystallization of methylammonium antimony iodide for efficient lead-free perovskite solar cells

The rapid development of perovskite solar cells (PSCs) has triggered a quest for lead (Pb)-free alternatives to improve their commercial viability. One such non-lead material, the methylammonium antimony iodide zero-dimensional dimer (CH3NH3)(3)Sb2I9, was reported recently, but with a low photo conversion efficiency (PCE) resulting from its poor surface morphology (many pinholes; amorphous nature). In this study, we employed anti-solvent treatment to improve the surface morphology of the Sb-based dimer by speeding up heterogeneous nucleation. We also incorporated an interlayer that acted as a favorable hydrophobic scaffold for the growth of large-grain (CH3NH3)(3)Sb2I9 crystals, thereby decreasing the number of the voids and increasing the film quality. We achieved a champion efficiency of 2.77%-a large improvement over the efficiencies reported previously. Using the techniques employed herein to prepare new perovskite-like materials, Sb-based photoabsorbers might become promising replacements for Pb-based perovskites.