Abstract: Disclosed are an organic proton-type ionic liquid, a film with a two-dimensional perovskite pure-phase quantum well structure, a preparation method and use thereof. The chemical formula of the organic proton-type alkylamine acetate ionic liquid is RNH3+—RCOO?, where R represents an alkyl group of C4-8 or a phenyl group, preferably, the chemical formula of the organic proton-type alkylamine acetate ionic liquid is CH3(CH2)3NH3+—CH2COO?. The organic proton-type alkylamino acetate ionic liquid disclosed in the present disclosure can be used to prepare perovskite material, the prepared perovskite film thereby can form a pure-phase single quantum well, and the crystal grain size of the film can reach the level of micrometers or even millimeters.