Acetate Anion Assisted Crystal Orientation Reconstruction in Organic–Inorganic Lead Halide Perovskite

The crystalline reconstruction along (112)/(200) planes rather than (110)/(002) planes of methylammonium lead iodide (MAPbI₃) is realized via an alternative one-step fabrication protocol that does not use the antisolvent dripping process, where methylammonium acetate (MAAc) is incorporated into the precursor solution. It is disclosed that the MAAc additive causes the modulation of the initial orientation of PbI₂ from (001) to (101) via formation of the intermediate adduct of PbI₂·MAAc, and the sequential deconstruction-reconstruction procedures result in dense perovskite films composed of large grains along (112)/(200) planes, differing from the needle-like crystallites along (110)/(002) planes constructed without MAAc assistance. The resultant films present superior optoelectronic properties, and corresponding solar cells with efficiency as high as 18.91% have been achieved at the MAAc content of 11%. Furthermore, anisotropic properties have been observed with respect to different crystal orientation, which also plays a crucial role in device performance