Synthesis And Electroluminescent Properties Of Phosphorescent Ruthenium Complexes

Ruthenium complexes especially the ruthenium polypyridine complexes are one of the widely studied light-emitting metal complexes in the world now. They are paid much attention to in many fields such as chemical sensor, chemistry (electrochemistry) analysis, catalyze, light-emitting device and so on. The synthesis of ruthenium complex is an important task, and many new complexes with different properties are synthesized and utilized now. To search for the relationship between structure and properties of ruthenium complexes is one of the crucial problems for scientists. This thesis is focused on this problem, and also contains some study of the light-emitting diodes based on these complexes.In chapter 2, we focused on the obtaining of high efficiency and red emitted ruthenium complexes. Two parts to constitute the complex: the ligand and the counterion were studied, and their structures were changed to adjust the electron structure of complex. The new polypyridine complexes of Ru-Fbpy-bpy, Ru-Fbpy-dpp, Ru-Fphen-dpp, Ru-Fdpp-dpp, Ru-Fdpp with rigid 3, 5-difluoro-benzene substitution and Ru-R2, Ru-R4 with flexible ester substitutions were synthesized. The study on the photophysical and electrochemistry properties of these complexes shows that the structure of ligand (including the type and site of substitution) affects the electron structure of the complex (HOMO and LUMO) greatly: the electron-withdrawing substitution can lower both the LUMO and HOMO level, and decrease the Eg of complex. The F atom favors a lifetime increase and high efficiency, while ester substitution improves the solubility of complex. The substitution on the opposite sites of N weakens the coordination bond and raises HOMO. The LUMO of central symmetrical complex is distributed on all the three ligands. Meanwhile, five ruthenium complexes with different counter anions Ru(dpp)3Cl2, Ru(dpp)3(BF4)2, Ru(dpp)3(PF6)2, Ru(dpp)3(ClO4)2 and Ru(dpp)3(AsF6)2 were synthesized. Their basic properties and the EL properties show that the ion-ion interaction makes great effect on the excited state of complex and charge transport properties in EL devices. The complex Ru(dpp)3(AsF6)2 with large anion exhibits higher PL efficiency and better EL performance than the others. These researches provide proofs for further obtaining high efficiency and red ruthenium complexes as well as the OLED based on them.In chapter 3, to obtain the good charge injection and transport ruthenium complexes, we introduce carbazole groupe to the peripheral of ester-bipyridine ligand, and synthesized new complexes Ru-Cz2 and Ru-Cz4. The photophysical experiment showed that these complexes exhibit the highest MLCT absorption at 480 nm, and their emission in solution are around 660 and 658 nm, respectively. The introduction of carbazole has little effect on the light emitting properties. Electrochemistry experiment showed that carbazole lowers the HOMO level of complexes and makes the hole injection much easier. Furthermore, the new complexes possess the ability of electrpolymerization because of the electroactive carbazole. We successfully fabricated red electrophosphorescent diodes by electrodeposition method using the complex Ru-Cz4. The device started to emit at 6 V, and the highest efficiency is 3.9 cd/A, which is better than the diode fabricated by commonly used method. In chapter 4, to obtain high efficient and red emitted OLEDs, we fabricated diodes based on the ruthenium complexes synthesized above, and optimized the structure of diode from the aspects of host, the concentration of guest, electron transport layer, hole blocking layer and so on. Among all the ruthemium complexes, Ru-R4 exhibits the best EL performance. The diode ITO/PEDOT/PVK-PBD:Ru-R4/TPBI/Ba/Al showed the highest efficiency of 16.7 cd/A and the EQE of 15.3% with the brightness maximum of 6800 cd/m2. The diode was red emitted and the CIE coordination is (0.63, 0.34). The host properties of fluorene oligomers and Si-contained polymers are further studied. The result shows that the main factor for high efficient diode is the charge balance of host materials.