Two-step dipping technique for the preparation of organic-inorganic

Abstract

A convenient two-step dipping technique for preparing high-quality thin films of a variety of perovskites is provided by the invention. Thin films of Mi.sub.2 (M=Pb, Sn) were first prepared by vacuum-depositing MI.sub.2 onto ash glass or quart substrates, which were subsequently dipped into a solution containing the desired organic ammonium cation for a short period of time. Using this technique, thin films of different layered organic-inorganic perovskites (RNH.sub.3).sub.2 (CH.sub.3 NH.sub.3).sub.n-1 M.sub.n I.sub.3n+1 (R=butyl, phenethyl; M=Pb, Sn; and n=1, 2) and three-dimensional perovskites CH.sub.3 NH.sub.3 MI.sub.3 (M=Pb, Sn; i.e. n=.infin.) were successfully prepared at room temperature. The lattice constants of these dip-processed perovskites are very similar to those of the corresponding compounds prepared by solution-growth or by solid state reactions. The layered perovskite thin films possess strong photoluminescence, distributed uniformly across the film areas. Similar results are achieved starting from spin-coated MI.sub.2 films, which were dipped into appropriate solutions of the organic ammonium cations. The process of the invention can be used for a variety of organics and inorganics, even if they have incompatible solubility characteristics or even if the organic component is susceptible to thermal decomposition on heating. Thin perovskite films prepared by the method are attractive candidates for emitter materials in electroluminescent devices.