Papers by Author: L.L. Guo

Abstract: An organic–inorganic hybrid perovskite (C₆H₅CH₂NH₃)₂CuCl₄was synthesized successfully by solution method at room temperature and the thin film of (C₆H₅CH₂NH₃)₂CuCl₄ was also prepared by spin-coating on the quartz substrate. The perovskite and the film were characterized with X-ray diffraction (XRD), Scan electronic microscope (SEM), Atomic force microscope (AFM), Fourier transform infrared spectroscopy and Thermo Gravimetric Analyzer. Results show that the obtained perovskite has unique layer structure and good thermal stability with melting point around 243.3°C. And the prepared film appears very smooth, continuous and uniform with a grain size of 0.1μm, highly oriented with the (0 0 l) planes perpendicular to the substrate surface. Its optical photoluminescence spectrum mainly depends on the inorganic part so the bandgap can be tuned by changing the inorganic composition. The carrier mobility is around 0.26cm²V^-1S^-1 , which indicates its potential application in field effect transistor with improved film quality.

Abstract: This paper focuses on the influence of interactions between different species in hybrids (CnH2n+1NH3)2MCl4 (M = Mn, Cu; n =2,4,6,8,10) on the structural stabilities. DSC-TG curves were used to find out the onset and the end decomposition temperatures. The results show that the hybrids of M =Cu start to decompose at about 210 centigrade degrees, average 25 centigrade degrees lower than that of M=Mn. The end temperatures of M=Cu are also lower. This suggests that in this case the thermal stabilities of the hybrids would be governed by the interactions between the organic and inorganic species and are little affected by weak Van de Waals interactions between the organic and organic species.

Abstract: Thin films of organic-inorganic hybrids (CnH2n+1NH3)2PbX4(X=Cl, Br, I; n=4,6,8,10) were prepared by the spin-coating method. The influences of annealing temperature on the crystal structure of the films were analyzed by X-ray diffraction(XRD). The surface morphology of the films were observed using scanning electronic microscope(SEM). The room-temperature UV-Vis absorption spectra of the films were employed to examine the effect on the optical properties of different elements X (X=Cl,Br,I), and varying n from 4 to 10, respectively. The results showed that a significant red shift of the absorption peak was observed for different X in inorganic layers, and the position of the exciton absorption peaks did not shift obviously with the increasing of the alkyl chain length in organic layers. The results suggested that the exciton absorption arise from electronic transitions within the inorganic layer, rather than from the organic layer.

Abstract: This paper focuses on the structural change and the thermochromism of the phase transition of the hybrid (C12H25NH3)2FeCl4. The temperature and the structures of the phase transition is investigated by a thermal gravimetry (TG) and differential scanning calorimetry (DSC), an infrared spectra (IR) and X-ray diffraction (XRD) patterns. The UV adsorption spectra account for the thermochromism. The results suggest that the reversible phase transition arises from the structural changes of the organic chains. The thermochromism is presumably due to the electrons redistribution on the levels and to the energy transition to translational and rotational motions of the organic chains.

Abstract: The organic-inorganic hybrid compounds have attracted much attention for their interesting structures and various properties. In present work, we concentrated on the band structures of the hybrid compound (C4H9NH3)2GeI4 and tried to find out the relations between the geometry structure and the properties. The hybrid’s primitive cell was large and including too many atoms, so it was difficult to have a direct and clear analysis on the band structure. The hybrids’ DOS and PDOS were analyzed instead, as it was another effective way to analyze the band structure of the hybrid especially when the band structure was complicated. The model of (C4H9NH3)2GeI4 was set up, and the program based on the first principle had been employed to calculate its band structure. The difference of iodine’s PDOS caused by structure was also discussed.