Zinc oxide (ZnO) is a semiconductor with various physicochemical properties allowing its use in a wide range of technological applications. The aim of this work is to study nanocrystalline ZnO thin-film deposited using zinc salt which is dissolved in pure ionic liquids (ILs). The latter play a dual role: solvent and supporting electrolyte. Most of ILs have a large electrochemical window and sufficient ionic conductivity. In this work, four hydrophobic ILs, based on 1-alkyl-3-methylimidazoliums bis(trifluoromethylsulfonyl)imide were synthetized and characterized to highlight the effect of the length of the cationic alkyl chain on the morphological, structural and optical properties of nanocrystalline ZnO deposits. Grain growth and its arrangement are affected by the length of the cation alkyl chain of ILs, that act as model agents during electroplating. The electrochemical properties of the produced thin layers were also studied.