Lead halide perovskites have attracted huge interest for their tremendous optical properties. However, their development is limited by lead toxicity and by an insufficient stability. We proposed recently a simple, new antisolvent precipitation route to achieve zinc-doped perovskite-inspired manganese halides with a formula Cs3ZnxMn1-xBr5. In the present paper, the influence of the atomic ratio R introduced during the synthesis, with , on the structure, morphology and optical properties of the material is investigated. Higher phase purity and best optical performances were obtained for the stoichiometric ratio, R 3. It was shown that when R is inferior to 3, the presence of two by-products, platelet-like Cs2ZnxMn1-xBr4 and of Cs2MnBr4.2H2O, is evidenced along with a lower internal quantum yield (iQY). Results show that adding a washing step with a polar solvent increases the iQY under blue excitation from 41 to 59 %. This has been correlated with a preferential dissolution of above-mentioned impurities and with an improvement in the material crystallinity.