| 8-hydroxyquinoline metal complexes have been widely used in organic light-emitting diodes and other organic electronic devices in view of their good thermal stability and high fluorescence quantum effects. Recently, it is found that the spin relaxation times in organic semiconductors are extremely long partially because of their weak spin orbit coupling and weak hyperfine interactions, which makes them ideal for spin-polarized electron injection and transport applications. However, the experimental spin diffusion lengths in organic films are greatly shorter than the theoretical expection. The low carrier mobility related to disorders, defects, impurities, and traps in amorphous organic films in organic devices prepared by vacuum deposition or spin coating may be responsible for the decrease in spin diffusion length. This problem can be, at least partially, solved by using organic crystals in which disorders, defects, traps and impurities are minimized instead of amorphous films. From this point of view, it is highly desired to investigate high quality organic crystals for the use of organic spintronic devices. In this thesis, crystalline 8-hydroxyquinoline zinc and 8-hydroxyquinoline copper were prepared by using physical vapor transport (PVT), annealing and solution method, the structural and optical properties of the prepared crystals are also investigated.The detailed contents and main results are given below:Firstly,8-hydroxyquinoline zinc crystals were prepared using the method of PVT. The structural properties and the qualities of the prepared Znq2 crystals were studied by XRD and FTIR. Subsequently, the photoluminescence (PL) spectra of the Znq2 crystals and thin films were studied. The PLpeaks of the Znq2 crystals were located at 535 nm. There was no big difference between the PL spectra of the Znq2 thin film and crystals.Secondly, Znq2 crystals were prepared by annealing Znq2 films in an argon environment. The Znq2 films were prepared by the method of thermal evaporation deposition. The roughness of the films was tested by using AFM. The images showed that the quality of the film was good. Znq2 crystals were generated when the film were annealed in an argon environment. The structural properties of the prepared Znq2 crystals were studied by FTIR. The luminous intensity of the after-annealing Znq2 became stronger by the PL spectrum. The reason may be the interactions between molecules, such as π-π stacking and hydrogen bond, became stronger during the process of the crystal growth.Finally,8-hydroxyquinoline copper crystals were prepared using solution method. Then the morphology, structure and optical properties of the crystals were analyzed in-depth. Chloroform was chosen as the organic solvent, three different concentrations of Cuq2 solutions were made. The Cuq2 molecules were self-assembly as the volatilization of chloroform, and hexahedral crystals were generated. A possible growth mechanism was proposed in this paper. The structural properties and the qualities of the prepared Cuq2 crystals were studied by XRD and FTIR. Subsequently, the PL spectra of the Cuq2 crystals and thin films were studied. The light emitting area of Cuq2 mainly located in green zone. A new light emitting peak was observed at 705 nm in crystals. It may be caused by the transition from the triplet state to the ground state. The luminous intensity became weaken when the temperature rised. |
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