We report here two topics on the construction of organic/inorganic quantum-well materials based on metal halide-based layer perovskite having an alternate layer structure consisting of an organic ammonium layer and a metal halide semiconductor layer. The first topic is the construction of new organic/inorganic quantum-well materials incorporated with functionalized ammonium molecules, which possess chromophores such as naphthalene and azobenzene, as an organic layer. In the second topic, we demonstrate a new method for the preparation of metal halide-based layer perovskite quantum-wells by using intercalation of organic ammonium molecules.