Two-dimensional perovskite templates for durable, efficient formamidinium perovskite solar cells

Abstract

We present a design strategy for fabricating ultrastable phase-pure films of formamidinium lead iodide (FAPbI(3)) by lattice templating using specific two-dimensional (2D) perovskites with FA as the cage cation. When a pure FAPbI(3) precursor solution is brought in contact with the 2D perovskite, the black phase forms preferentially at 100 degrees C, much lower than the standard FAPbI(3) annealing temperature of 150 degrees C. X-ray diffraction and optical spectroscopy suggest that the resulting FAPbI(3) film compresses slightly to acquire the (011) interplanar distances of the 2D perovskite seed. The 2D-templated bulk FAPbI(3) films exhibited an efficiency of 24.1% in a p-i-n architecture with 0.5-square centimeter active area and an exceptional durability, retaining 97% of their initial efficiency after 1000 hours under 85 degrees C and maximum power point tracking.