Phosphorescence Properties Of D-A Organic Molecules In Crystalline And Polymer

Pure organic room temperature phosphorescent materials(PORTP)and fluorescent materials belong to the phenomenon of photoluminescence.They have extensive research value in the fields of biomedicine,lighting,anti-counterfeiting and optoelectronic devices.Therefore,they have become a hot spot for scientists to explore.PORTP itself has a large Stokes shift,and has the advantages of high penetration,high detection sensitivity,and less damage to biological samples in biological applications.Compared with metal-based organic phosphorescent materials,PORTP also has obvious defects.Its triplet excitons are very sensitive to oxygen and humidity,and the molecular orbital coupling ability(SOC)is weak,resulting in weak phosphorescence emission.In order to solve this shortcoming and give full play to the advantages of PORTP,scientists have found several effective methods to obtain high-efficiency and long-life PORTP phosphorescent materials,such as crystallization,polymers doping,etc.,in the currently published articles,the properties of phosphorescent materials have been greatly improved.In this paper,the phosphorescence properties of donor-acceptor(D-A)organic molecules in crystalline states and polymers are studied.The main contents and conclusions are as follows:(1)Single D-A structure molecule with carbazole group and cyano group was designed and synthesized,and its crystalline molecular structure properties were tested.Subsequently,the D-A structure molecules were doped into the rigid polymer matrix polymethyl methacrylate(PMMA),thermoplastic processing was performed to orient the internal small organic molecules,and various PMMA polymer matrix films were prepared.After doping,the phosphorescence emission of the PMMA polymer film was improved to different degrees,among which 2X4 Q obtained a bright,blue long afterglow emission of up to 8.4s,and the phosphorescence lifetime of 2X4 Q reached 1010 ms.The rigid polymer matrix can suppress the quenching of triplet excitons by oxygen and moisture,reducing nonradiative transitions.The D-A structure molecule was doped into thermoplastic elastomer(SIS),and the phosphorescence properties of SIS flakes and PMMA flakes were compared,and it was found that the afterglow of SIS flakes was far inferior to that of rigid substrates,and it was believed that flexible SIS had relatively weak inhibition of oxygen and Moisture ability,so that the ability to suppress triplet exciton quenching becomes poor.(2)D-A molecules are synthesized and named as 1Dm CZ,2Do CZ,and 3Dom CZ,respectively.Through single crystal analysis of the three isomer molecules,it was found that the twisted molecule 1Dm CZ has a higher phosphorescence lifetime(535.4 ms),and the phosphorescence lifetime of the larger twisted 2Do CZ molecule is only 341.5 ms.In order to obtain materials with good phosphorescence properties,three isomer molecules were doped into the PMMA matrix,and oxygen and moisture were removed by thermoplastic processing.It was found that the phosphorescence efficiency of 1Dm CZ doped flakes increased from the original 2% to 9.8%,an increase of 4 times.This is because polymer doping reduces the free volume of molecules,suppresses molecular motion,and enhances the efficiency and intensity of phosphorescence emission.(3)Artificially synthesized carbazole and prepared laboratory carbazole derivatives,and compared with the phosphorescence properties of commercial carbazole derivatives,it was found that the phosphorescence properties of artificially synthesized carbazole derivatives lacking carbazole isomers significantly deteriorated.After testing its lowtemperature intrinsic phosphorescence and room-temperature phosphorescence,it is believed that the crystalline state of artificially synthesized laboratory carbazole derivatives cannot effectively suppress triplet exciton quenching,while trace amounts of doped carbazole isomers undergo energy transfer with the host material.,forming a charge transfer state and generating strong intermolecular interactions,thereby inhibiting the movement of molecules,inhibiting thermal deactivation,and producing super-strong phosphorescence emission.