Synthesis And Properties Of Triazine Phosphorescent Host Material

Since Dr.Deng Qingyun invented organic light-emitting diodes(OLED)in 1987,research in related fields such as organic light-emitting materials has flourished.Compared with traditional OLED,phosphorescent organic light-emitting diodes(PhOLED)can capture all singlet and triplet state excitons by using heavy metals to enhance the system to cross,so that PhOLED can theoretically achieve 100% external quantum efficiency.In organic electroluminescent materials,the host material of the luminescent layer is crucial.Phosphorescent host materials generally need large HOMO-LUMO energy gap and triplet state energy level higher than that of guest materials,so that energy can be completely transferred to guest materials.The host material based on dibenzofuran structure has high triplet state energy and bipolar carrier transport characteristics,and the host material based on triazine structure has good electron transport ability due to its high electron deficient configuration;Materials based on carbazole groups have good hole transport ability.In this thesis,three phosphorescent host materials were designed and synthesized using dibenzofuran,carbazole,and biphenyl as substituents,and 1,3,5-triazine as the core skeleton.Explore the synthesis methods and characterize the synthesized products by mass spectrometry and nuclear magnetic resonance;Perform DFT calculations and energy level structure tests on the prepared materials,and study their photophysical properties and thermal stability.The experimental and computational results show that the three phosphorescent host materials all have a deep energy gap of 3.37-3.41 eV,a high triplet energy level of 2.45-2.68 eV,good photophysical properties,a glass transition temperature above 140℃ and a high thermal decomposition temperature above 500℃;This indicates that the three materials have good potential to become the phosphorescent host materials in OLED devices.Using the prepared material as the host material for the luminescent layer of OLED devices,a matching hierarchical material is selected to make the OLED green top emitting device,and the performance of the prepared device is studied.Among them,the operating voltages of the three devices are all between 3.74 V and 3.90 V,with external quantum efficiencies of up to 38.55%,31.51%,and 33.51%,respectively.The emission spectrum and color coordinates are located at the center of the green light,and the device has a lifespan of over 20 hours.To improve the lifespan and efficiency of the device,P-type host material and the synthesized phosphorescent host material were selected for multiple proportions of doping optimization.The performance test results of the device indicate that the efficiency of the doped device has been slightly improved,and the lifespan has been greatly improved.When the doping ratio is 1:1,the performance improvement of the device is the highest,with a maximum lifetime improvement of 60.57%.The optimization results of the device indicate that due to the introduction of P-type host material,the electronic and hole transmission capabilities of the device are more balanced,resulting in a significant improvement in the overall performance and device lifespan of the device.