Design And Synthesis Of Europium Complexes And Study On Their Luminescent Properties

The status of organic / polymeric europium complexes used as electroluminescent materials and their light-emitting devices are reviewed in this dissertation. The organic / polymeric europium complexes and their electroluminescent properties are carried out in order to solve current problems, such as low luminous efficiency and brightness, of europium complexes in their devices. The key studies results are listed below:1. Phenanthroline ligand was tuned by incorporating triphenylamine group with hole-transporting nature and oxadiazole groups with electron-transporting nature into phenanthroline, which can help their europium complexes to have improved carrier-transporting property and increased luminous efficiency. Six europium complexes made with excellent carrier-transporting property have not been reported yet. The molecular structures of these tuned phenanthroline derivatives with triphenylamine and oxadiazole groups and their europium complexes were characterized by element analysis and 1H NMR.2. The UV absorption and photoluminescence (PL) properties of phenanthroline derivatives with triphenylamine and oxadiazole groups and their europium complexes were investigated. These europium complexes display intense UV absorption and photoluminescence (PL) properties. The PL results from emission of Eu3+ ion in their pure thin films. A maximum PL wavelength is 612 nm and a full width at half maximum (FWHM) is from 9 nm to 15 nm for the PL of these europium complexes, respectively.3. Two-layered polymeric light-emitting devices with red emission were fabricated using triphenylamine- and oxadiazole-based europium complexes as emitters. The devices exhibited strong electroluminescence resulted from emission of Eu3+ ion with a maximum emission wavelength of 611 nm ~ 615 nm and a FWHM of 9 nm ~15 nm. The maximum external quantum efficiency (EQE) of 2.5% and a peak brightness of 1333 cd/m2 are achieved in these devices. The values are higher than those values in europium complexes-doped PLEDs reported previously.4. Six kinds of copolymers and their europium complexes were synthesized by Suzuki reactions. The copolymers contain carbazole-phenanthroline copolymers, carbazole- phenanthroline-oxadiazole copolymers, fluorene-phenanthroline co-polymers, fluorene- phenanthroline-oxadiazole copolymers, benzene-phenanthroline copolymers and benzene- phenanthroline-oxadiazole copolymers. The UV absorption and photoluminescence (PL) properties of these copolymers and their europium complexes, as well as electroluminescence (EL) properties of these europium complexes were investigated. The influence of molecular structures of these copolymers used as neutral ligands on the optoelectronic properties of these europium complexes was also investigated.5. The copolymers and their europium complexes exhibited good solubility and dispersibility in CH3Cl. These europium complexes containing various co-polymers exhibited intense PL in the devices. A maximum PL wavelength is 611 nm ~ 615 nm and a FWHM is from 10 nm to 14 nm for the PL of these europium complexes-doped devices, respectively. The PL emission result from 5D0→7F2 transition of Eu3+ ion. The device using the europium complex Eu-PFOXDPh0.30 as an emitter displayed a maximum EQE of 0.071% and a peak brightness of 2.6 cd/m2. These values are comparable to those values in polymeric europium complexes-based PLEDs reported before. However, the devices using the europium complexes with these copolymers as emitters have not displayed satisfactory luminous efficiency. It is necessary for high-efficiency PLEDs to further optimize device configuration.6. The result of optoelectronic properties of these europium complexes show that the molecular design is crucial to achieve europium complexes with high- efficiency emission. The luminous properties of europium complexes can be optimized by tuning the molecular structure of phenanthroline used as a neutral ligand in europium complexes. The europium complexes containing copolymers can display high-efficiency PL rather than EL. Therefore, the EL properties of the europium complexes containing copolymers need be further investigated. This study is significant in order to further study on influence of neutral ligands with functionalized groups on the EL properties of europium complexes and improve carrier-transporting nature and luminous efficiency of europium complexes, as well as achieve novel europium complexes.