Organic Phosphorescence Molecules Of Phenylcarbazoles: Design,Synthesis And Performance Studies

Recently,researches on purely organic light-emitting materials with room-temperature phosphorescence emission and their potential applications have become the current hot spots in organic electronics.However,there are still some limitations in the realization of organic room temperature phosphorescence,such as spin-forbidden exciton transition,requirement of ultraviolet excitation,short phosphorescence luminescent lifetime,low quantum efficiency,and lack of effective manners to adjust the intersystem crossing process and molecular stacking simultaneously.This thesis focuses on the current difficulties in the design and preparation of organic room temperature phosphorescent materials,and novel design strategies were proposed to adjust the room temperature phosphorescent properties of the materials:1.A series of phenylcarbazole molecules modified with bromine atoms are designed,aimed to use the synergistic effect of heavy atoms and heteroatoms to enhance the spin orbit coupling of the conjugated systems.Direct absorption of S₀?T₁ was realized to achieve room temperature phosphorescence emission.Through systematic experiments and theoretical calculations,the triplet direct absorption was verified and proceed to be an excellent candidate for improving the room temperature phosphorescence quantum efficiency.Therefore,the phosphorescence lifetime and phosphorescence quantum efficiency were increased by 2.5 times and 15.6 times compared to that on the excitation of UV light.According to the room temperature phosphorescence properties of the material,a double encryption device with time resolution and color resolution was succeeded for the first time.2.A series ultralong room temperature phosphorescent materials based on cyanohalogen modification of phenylcarbazole were prepared.The n-?*transition of lone pair electrons if the cyano pseudohalogens is used to promote the intersystem crossing process.Also,the cyano substituent effect controls the stacking structure of the molecules.By changing the modification sites and the number of modification groups,it was found that the molecules modified at positions3 and 6 of carbazole exhibit longer lifetime of the phenylcarbazoles.The relationship between room temperature phosphorescent luminescence properties of the material and the stacked structure was analyzed using molecular exciton theory,which verified that the phosphorescent lifetime is in positive correlation with H-aggregated structure of the material.3.Two organic room temperature phosphorescent molecules containing benzophenone structure were designed and synthesized.By introducing a carbonyl group(C=O)group in the conjugated system of organic room temperature phosphorescent molecules,the molecules form benzophenone units and the conjugated structure of the molecule can be changed.Therefore,the molecule has a distorted spatial configuration and effective charge separation is achieved and the molecules modified with bromine atoms show ultralong room temperature phosphorescence emission with a lifetime of 307 milliseconds.It was found that the donor-acceptor(D-A)structure constructed by introducing cyano groups,exhibits small single-triplet energy gap(?E_ST),resulting in aggregation-induced delayed fluorescence and facilitated channels of reverse intersystem crossing for multi-mode light-emitting properties.Non-doped OLEDs was also fabricated to test its potential device application prospects.