Organic-inorganic hybrids are a technologically important class of materials, offering the possibility of combining useful properties of both organic and inorganic components within a single molecular composite. Optical and electrical properties of organic materials, for example, can be tuned relatively easily by modifying their molecular structure. Their ease of processing, plasticity, and low price make organic materials attractive for a number of applications. Lack of robustness, thermal stability, and low electrical mobility, however, inhibit their use in many of the same applications. These latter properties are offered by inorganic materials. By synthesizing organic-inorganic composites, the best of both worlds can potentially be obtained within a single material.
The layered organic-inorganic perovskites are a subclass of the organic-inorganic hybrids, and have recently attracted substantial interest due to their potential for unique electrical, magnetic and optical properties. The basic building component of this family is the inorganic ABX.sub.3 perovskite structure. By replacing the A inorganic cation with an organic one, organic-inorganic hybrid perovskite compounds are formed. In these ionic compounds the organic component is an intimate part of the structure since the structure actually depends on the organic component for charge neutrality. Therefore, the compounds exhibit specific stoichiometries. The layered (two-dimensional) A.sub.2 BX.sub.4, ABX.sub.4 and the one-dimensional A.sub.3 BX.sub.5, and A.sub.2 A'BX.sub.5 perovskites also exist and are considered derivatives of the three-dimensional parent family.
In these lower dimensionality compounds, exciton formation is observed within the inorganic sheets, with large binding energies (&gt;300 meV) and oscillator strength. Interesting physical properties such as strong room temperature photoluminescence, third harmonic generation, and polariton absorption arise from these excitons. The strong photoluminescence and the ability to tune the emission wavelength by means of incorporating different metal or halogen atoms in the structure make these perovskites attractive as emitter materials in electroluminescent devices, although currently such devices operate only at low temperature. Generally, simple organic cations such as aliphatic or single ring aromatic ammonium cations are used to form these structures. These cations are optically and electrically inert.
It is an object of the present invention to provide an organic-inorganic hybrid that incorporates a mixture of functional, optically active, luminescent dye molecules and optically inert molecules within the organic component of the structure. The dilution of the dye molecule within the organic component will reduce self-quenching interactions occurring between the dye molecules, which in turn will increase the luminescence yield.
It is another object of the present invention to provide an organic-inorganic material that is not random, but rather self assembles itself into a predictable arrangement of organic and inorganic components. This reduces the variability of luminescence and increases charge conduction between the inorganic and organic components.
It is a further object of the present invention to provide an organic-inorganic material that is readily deposited on a substrate by simple and inexpensive methods.