Synthesis And Characterization Of Deep-blue Iridium Dendrimers With Carbazole Dendrons

By integrating host and phosphor covalently in a molecular level, we have previouslydeveloped a series of blue, green and red iridium (Ir) dendrimers with self-host feature, andrealized highly efficient nondoped phosphorescent organic light-emitting diodes (PhOLEDs).However, there are few reports about the development of deep-blue Ir dendrimers. Thereforethe focus of this thesis is how to further extend this molecular design rule to deep-blueemission. With this idea in mind, a small molecular deep-blue Ir complex is selected as thecore tethered with carbazole dendrons via a non-conjugated linkage in order to exploitdeep-blue Ir dendrimers including homoleptic and heteroleptic structures. And detailedinvestigation has also been performed to demonstrate the effect of carbazole dendron on thephotophysical, electrochemical and electroluminescent properties.Firstly, using FCNIr as the emissive core, the homoleptic deep-blue Ir dendrimers IrG0,IrG1and IrG2with different generation carbazole dendrons are prepared. The emissionmaxima of IrG1and IrG2at449nm are independent of carbazole dendron, close to that ofIrG0(446nm). Nevertheless, both their solution photoluminescent quantum yields andHOMO levels are gradually increased with the increasing generation number. Among them,the first-generation dendrimer IrG1has the best nondoped device performance, revealing amaximum external efficiency of7.8%, a peak luminous efficiency of13.7cd/A and a peakpower efficiency of9.3lm/W together with CIE coordinates of (0.16,0.22).Subsequently, the corresponding heteroleptic deep-blue Ir dendrimers IrG0(acac),IrG1(acac) and IrG2(acac) are synthesized, which all contain the ancillary ligandacetylacetone. Compared with the homoleptic counterparts (449nm), the emission peaks ofthese heteroleptic dendrimers in solution are red-shifted towards460nm. When the generationnumber rises, interestingly, an obvious red-shift is observed for their PL spectra in solid states.For example, the emission maximum is up from463nm of IrG0(acac) to472nm of IrG1(acac)and488nm of IrG2(acac). Furthermore, the second-generation dendrimer IrG2(acac) is foundto exhibit aggregate enhanced emission (AEE) to some extent.