Design, Synthesis And Study Of Double Substituted Equilibrium Regulating High Efficient And Long Life Pure Organic Room Temperature Phosphorescent Materials

In recent years,metal-based phosphorescence materials,which are expensive and biotoxic,have been gradually replaced by pure organic room temperature phosphorescence(PORTP)materials that are environmentally and biofriendly.The development of PORTP materials has received comprehensive attention.Although after long-term efforts to research,scholars have been designed and synthesized a number of PURTP materials,but due to the restrictions of molecular,most of the materials have long life(??100 ms)or excellent properties of high efficiency(??5%)unilaterally.So we designed and synthesized two serts of isomers which have double-substituted functional groups to balance adjustment RTP life and efficiency of themselves.In this work,commercial carbazole(CCZ),a classic material of RTP with a long life,was modified by heavy atom Br and–CN/-CONH₂ containing heteroatomic groups,at the same time,benzene ring is used to extend the degree of conjugation.Two sets of isomeric systems achieve equilibrium regulation of phospherscence efficiency and life by changes of Br substitution sites.Through the characterization and crystal analysis of various aspects of molecular photophysical properties,we can understand the profound influence of different molecular configurations and molecular interactions in crystals on the properties of materials RTP.The results showed that all molecules exhibited the phenomenon of double emission of room temperature phosphorescence and fluorescence,and had a long phosphorescence lifetime more than 100 ms.Among them,the phosphorescence quantum yields of 5X3Q,5X3J,6X3Q and 6X3J were all more than 5%,which achieved the goal of high efficiency and long life phosphorescence.Through the single crystal analysis of each molecule,we found that the more intermolecular forces,the stronger the molecular force,the more conducive to the material RTP luminescence.In the research,different wavelength lights were used to achieve the regulation of material RTP performance.It is also found that 5X3J and 6X3J materials can be excited by460-520 nm light source,showing a bright yellow afterglow.We propose that the sample is excited by long-wave excitation light,and the triplet excitons are contributed by the direct spin inversion process of S₀?T_n.Therefore,with the increase of excitation wavelength,the phosphorescence gradually decreases,which is a new exploration for the excitation of long-wavelength phosphor materials.Recent studies have found that due to the inevitable problems in the purification process of commercial carbazole,it contains a small amount of its isomer,benzo indole,which synergizes carbazole to produce long-lasting RTP luminescence.In addition,the lab-prepared carbazole no longer exhibits RTP properties^[1].For this reason,we synthesized carbazole(LCZ)by our own.By comparing the photophysical properties of materials with the same structure from different carbazole sources,it was found that the performance of LCZ and its derivatives was indeed inferior to that of CCZ and its derivatives at room temperature,but the phosphorescent properties of LCZ and its derivatives would be greatly improved at low temperature.It is concluded that the isomers of carbazole can inhibit thermal deactivation at room temperature and provide stable triplet exciton stabilization.