Our DoE began with the selection of the parameter space. The main focus was oriented on generating new quasi-2D RPPs. The variables considered are shown in Figure . This defines a parameter space with: 10 × 4 × 5 × 5 × 4 × 4 = 16,000 possible permutations. To ensure reproducibility, all the halide salts of 2D and 3D cations were mixed in stoichiometric ratios to obtain the RPP solutions, resulting in films with specified n-numbers, cation, and halide compositions. The drop-casted solutions further contained additives or alternatively were additive-free (denoted as "none"). The temperature of the perovskite annealing step was also varied. This selection permitted for semi-random list of 100 recipes of theoretically highperforming RPPs. See Supplementary Information for further experimental details. AVA is 5-amminovaleric acid, PEA is phentylammonium, GUA is guanidinium, FA is formamidinium, MA is methylammonium, I is iodide, Br is bromide, MASCN is methylammonium thiocyanate, MACl is methylammonium chloride (where LC is low concentration and HC is high concentration), HI is iodic acid, and None stands for equivalent pure solvent used for dissolving the rest of additives. The RPP film post-annealing was also a varied parameter as denoted.