Synthesis, Structure And Characterization Of Layered Perovskite-typed Organic-inorganic Hybrids Materials

Layered perovskite-type organic-inorganic hybrids are a type of new materials which compounded by organic and inorganic units on the molecular level, they have natural quantum well structure. The appearances of hybrids give the possibilities of combining the useful properties of organic and inorganic materials on the molecular scale. They provide an unprecedented opportunity for deeply understand the laws of the structure forming and the relationship between structure and properties.However, the current hybrids, due to the structure and properties (such as carrier mobility, etc.) can not meet the requirements of practical device applications, largely limited the development of hybrids. In the quantum well structure of hybrids, the excitons are limited in the 2-D inorganic perovskite layer, so we predict that the structure of inorganic perovskite layer will greatly affect the band gap of the quantum well,thus affecting the properties (such as the conductive properties and optical properties)of the materials. Therefore, systematically study the mono-layered and multi-layered perovskite-typed hybrids on the structures and the structure forming rules well be very important.This dissertation focuses on the synthesis and structure of hybrids (R-NH3)2(CH3NH3)n-1PbnI3n+1(n=1,2) (n=1,2). We choose butylamine,β-phenylethylamine and dodecylamine as the organic units, PbI2 based mono-layered and bi-layered perovskite-typed organic-inorganic hybrids were successfully synthesized by the reactions in solutions.The structures, chemical components and properties of the acquired products at room temperature were characterized and analyzed by X-ray diffraction, SEM, FTIR, TG-DSC and UV-is spectrum analysis. The results demonstrate that the XRD of the product powder have a high degree of preferred orientation along (002l) direction, all hybrids feature layered structures and the interlayer distance increases when the organic alkyl chain lengths increase. The calculated interlayer distance differences between the bi-layered and the mono-layered hybrids are almost the height of a [PbI6] octahedra. There are absorption peaks of Characteristic groups and chemical bonds of the theoretical structures in the FTIR, which supports the forecast structures of the products. The TG-DSC curves show a very complex process of thermal decomposition, the actual weight loss of the organic is almost the same with the theory weight loss, the breaking up temperature of the products obtained from the TG curves show that the breaking up temperature has a great relationship with the organic units in the hybrids. From the UV-vis spectrum of the products we can see that the number of layers of the inorganic perovskite layer has a direct impact on the band gap, the band gap of bi-layered structure is significantly less than the band gap of mono-layered structure. The effect of the organic to the band gap is not so large, compared to butylamine and dodecylamine system, the band gap of phenylethylamine system is a little smaller, indicating that the benzene ring in the organic units has a Fine-tuning effect to the band gap.