Vacuum Deposition of Triple-Halide Wide-Bandgap Perovskites Enabled by Sublimation of Mixed Organic-Halide Pellets

Controlling the sublimation of organic compounds during perovskite deposition via coevaporation is challenging. The sublimation behavior of these materials depends strongly on their purity, and their low sticking coefficient on sensors complicates deposition rate monitoring, hindering reproducibility, particularly when multiple organic sources are involved. We introduce a novel approach in which the precursor powder is pressed into a pellet, reducing material consumption and pressure fluctuation during coevaporation. This pellet can also incorporate multiple compounds, enabling, for example, the simultaneous sublimation of methyl-ammonium iodide and chloride from a single source. Combined with a Pb-(I_1-<i>x</i> Br _<i>x</i> )₂ source, this method makes it possible to deposit triple-halide MAPIBrCl perovskite films. We confirm the incorporation of chloride in the perovskite lattice, which proves to be beneficial for the charge transport properties of the film, increasing the fill factor in wide-bandgap solar cells. Using this approach, we achieved a champion PCE of 19.5% for a 1.66 eV bandgap perovskite.