Synthesis And Properties Of Dendritic Ionic Complexes Of Electroluminescent Materials

At present,most of the high-efficiency phosphorescent electroluminescent devices are prepared by vacuum evaporation.Compared with the evaporation preparation device,the wet preparation device can be used for large-screen display,and has more application prospects in the market.Therefore,a large number of wet doping devices have been developed to improve carrier transport performance by doping an electron transporting material and a hole transporting material in the light emitting layer.However,there are a series of problems in the doping system,such as poor stability of the mixed phase,poor reproducibility and cumbersome processing,so it is necessary to develop a wet undoped ruthenium complex system.The dendrimer not only has the molecular structure determined by small molecules and the good processing properties of the polymer,but also has excellent spatial isolation effect on the peripheral branches of the access,which provides a reliable guarantee for the preparation of wet processable devices.At present,most dendritic ruthenium complex materials are studied around neutral luminescent molecules,while ionic ruthenium complexes have been reported in wet devices.We mainly introduce branching groups into ionic steroids.The periphery of the material improves the wet film formation properties of the molecules and studies the effects of different peripheral branches on the luminescence properties of the materials.In this article,we mainly carry out related work from the following aspects:1.A series of yellow-green photoion-type dendritic steroid complexes G1,G2,G3and G4 were designed and synthesized by introducing a triazole-containing dendritic group around the benzoimidazole nucleus.Theoretical calculation shows that the LUMO orbital is distributed on the benzimidazole group,which makes the electron injection and transmission barrier smaller.At the same time,the peripheral branch group is beneficial to the improvement of hole transport performance,thus indicating the introduction of the periphery.Branches can coordinate carrier transport capabilities.In addition,through the comprehensive analysis of the obtained devices,it is known that the ionic ruthenium complexes G1,G2 and G3 have better film forming properties than the neutral ruthenium complex G4,stable physical properties,superior device performance,and the highest current efficiency reaches 48.9 cd/A.It is about 4 times the efficiency of the neutral germanium complex device,and the device efficiency belongs to the best efficiency range reported so far.The thermal decomposition temperature of the ionic ruthenium complex is higher than the corresponding neutral ruthenium complex,which is more beneficial to practical applications.At the same time,we compare the ionic complexes of the same type,and find that the device efficiency of the luminescent complex of the ionic ruthenium complex is higher than that of the corresponding dendritic iridium complex,and the device efficiency decreases with the increase of the peripheral branch trend.2.In the full-color display,the blue light material is indispensable.We use the sky blue ion-type ruthenium complex to study the luminescent nucleus.At the same time,in order to explore the influence of the branch group on the photoelectric properties of the ionic ruthenium complex,we still use the three azole-modified alkyl chain is used as a peripheral branch group to synthesize the corresponding ionic ruthenium complex.According to the relevant literature,we have selected suitable materials to synthesize the sky blue ruthenium complexes G5 and G6.By testing the above two ruthenium complexes,we can see that the two materials have excellent photophysical properties and electrochemical properties,and the excited state lifetime is 0.2?s.The?s is about the range of room temperature phosphorescence.The maximum emission wavelength is 470 nm,which indicates that the peripheral branch of the access does not affect the excited state of the luminescent core.The thermal decomposition temperatures are317°C and 352°C,respectively.The thermal stability is improved after the molecular weight is increased,and the bright voltage of the wet device is lower than 5 V,which proves that the molecular HOMO orbitals match the work function of the anode well.From the analysis of the undoped devices made by these two iridium complexes,the maximum brightness of the device is above 10000 cd/m~2,and the maximum current efficiency is 15.4 cd/A,indicating that these two materials have good luminescence properties.Comparing the wet device performance of the two ruthenium complexes,it is found that the performance of the device based on the luminescent core is better than that of the corresponding dendritic ruthenium complex,which is consistent with the law of the green light dendritic ruthenium complex studied in the previous study.The wet device performance of the complex decreases as the number of peripheral branches increases.