Design,Synthesis And Properties Of Red And Near Infrared Donor-Acceptor Type Organic Light-Emitting Materials

In recent years,the promising organic light-emitting diodes with red and near infrared(NIR)emission,which can not only be used for lighting,flat-panel displays but also for emerging technologies such as night vision devices,information security,optical communications,biomedicine,have caught increasing attention.However,according to the energy gap law,red especially NIR emitters usually suffer more serious non-radiative energy loss,which can accout for the relatively slower development and challenging of red and NIR emitters than blue and green emitters with wider band gap.Generally,constructing donor(D)-acceptor(A)molecules and utilizing intramolecular charge transfer mechanism can simplify the realization and regulation of red and NIR emission with facile synthetic routes.Thus in this thesis,we have explored the novel fluorenone derivatives with red emission and anthryleno[1,2-b]pyrazine derivatives with NIR emission.In chapter two,we have constructed two fluorenone-based TADF emitters named DMAC-FO and SPAC-FO.Compared with widely reported benzophenone acceptor,fluorenone exhibits stronger electron withdrawing ability owing to the extended conjugation skeleton.By introducing two acridine-based donor units at C3 and C6 sites of fluorenone,DMAC-FO and SPAC-FO exhibit strong intramolecular charge transfer and realize orange-red emission.Besides,the highly twisted molecular structures and well matched S1 and T1 states make two molecules can utilize both singlet and triplet excitons for the improvements of OLED device efficiency.As a result,DMAC-FO and SPAC-FO based devices have surpassed the 5%theoretical margin of conventional fluorescence devices.Moreover,compared with DMAC-FO,more stable configuration of spiro-acridine donor contributes to better performance of SPAC-FO based devices,which demonstrates that it is important to reduce non-radiative energy loss for long wavelength emission(red,especially NIR emission).In chapter three,we have proposed a novel acceptor anthryleno[1,2-b]pyrazine-2,3-dicarbonitrile core and constructed two NIR emitters,DCPA-TPA and DCPA-BBPA,by introducing aromatic amine donors.Compared with reported TPAAP,the extended πconjugation on accepter segment enhances the electronic withdrawing ability.Thus,DCPA-TPA and DCPA-BBPA exhibit narrower bandgaps and large dipole moments.Moreover,two emitters exhibit further redshift NIR emission from doped films to neat films with gradually enhanced surrounding polarity.Thus,the non-doped devices based on DCPA-TPA and DCPA-BBPA have exhibited real NIR emission:both onsets of them are above 700 nm and peaks are at 838 and 916 nm,respectively,which can hardly be perceived by human eyes.And it is well to notice that DCPA-TPA based non-doped device with further optimized structure have realized a high radiance of 20707 mW Sr-1 m-2,which is among the best performance of fluorescence NIR OLED devices with emission peak above 800 nm.Up to now,most fluorescence emitters with electroluminescence peak above 800 nm are 1,2,5-thiadiazole derivatives.This work has explored a new kind of anthryleno[1,2-b]pyrazine derivatives,which has held great promise for the realization of NIR emission and provided new guidance for development of highly-efficient NIR emitters.