| Organic light-emitting diodes?OLED?are paied much attention due to their features of high emission efficiency,wide viewing angle,low driving voltage and flexibility.However,the lack of high-performance organic electron transport materials all along restrains the development of organic electroluminescence devices.This thesis firstly constructed a series of phenyl benzimidazole derivatives with phosphine oxide as bridge group and studied the influence of the involvement of phosphine oxide groups on the optoelectronic properties.The investigation showed that their triplet energy levels?T1?are preserved as 2.97 eV,accompanied with the lowest unoccupied molecular orbital?LUMO?energy levels at-2.7 eV and electron mobilitis around 10-7-10-5 cm2 V-1 s-1,reflecting the favorable electron injection and transportation ability.In virtue of the steric effect of phosphine oxide group on suppressing interfacial exciton-polaron interaction,the high-efficiency blue phosphorescent OLEDs were achieved with the maximum current efficiency?CE?of47.3 cd A-1,power efficiency?PE?of 36.0 lm W-1 and external quantum efficiency of22.2%,which were two folds of those of phenyl benzimidazole analogues.A series of bisubstituted phenyl benzimidazole materials were further constructed by using phosphine oxide as peripheral groups.Their T1 energy was still preserved as2.97 eV.More phosphine oxide groups reduced their LUMOs to-2.8 to-3.0 eV and provided the stronger embedding effect on phenyl benzimidazole.With phosphine oxide substituted phenylbenzimidazole as ligands,a series of mononuclear,binuclear and trinuclear iridium complexes were synthesized.The internuclear interaction was restrained by phosphine oxide group,rendering the stronger emissive intensity without changing emissive color. |
PDF Full Text Request