Synthesis And Properties Of Thermally Activated Delayed Fluorescence Materials Based On Acridan Derivatives

Organic thermally actived delayed fluorescence(TADF)material has been attracted much attentions by the researchers in recent years because of their free of metal atoms,low cost and capacity of harvesting both singlet(S1)and triplet(T1)excitions.Although TADF materials have made huge progresses over the past several years,there are still some key scientific problems such as little material types,severe device efficiency roll-off and poor color purity which has a limitation for their commercial application.In order to further explore the relationship between TADF material and properties,a series of donor-acceptor(D-A)TADF materials based on acridine unit were designed and synthesized through reasonable molecular structure in this thesis.The main research contents of this thesis are as follows:(1)Two D-A compounds of OHOXD and BFOXD were designed and synthesized based on acridine and oxadiazole groups.The relationship of structure-property of both OHOXD and BFOXD were studied in detail.The results show that both compounds have good thermal stability with a decomposition temperature of>380 ~oC at 5%weight loss.The transient fluorescence spectra confirmed that both compounds OHOXD and BFOXD have TADF properties.Interestingly,compound OHOXD exhibits excited-state intramolecular proton transfer property.Both compounds exhibit sky-blue emission with the maximum emissive peak at 473 nm in solution and solid film.Using TADF compound CzAcSF as the host,the solution processable OLEDs were fabricated and achieved the maximum external quantum efficiencies(EQEs)of 12.1%and 20.1%for OHOXD-and BFOXD based device,respectively.(2)Employing acrding and triphenylamine as the donor units and disulfone derivatives as acceptor units,four crucifix-shaped compounds TPA-BPSB,DMAc-BPSB,MTPA-BPSB and MDMAc-BPSB were constructed.The results show that these crucifix-shaped compounds have good thermal stability.All these compounds present TADF character by transient fluorescence spectra.In toluene solution,the maximum emissive peaks of the four TADF materials were between 517 and 544 nm.The photoluminescence efficiencies of TPA-BPSB,DMAc-BPSB,MTPA-BPSB and MDMAc-BPSB are 92%,13%,88%and 10%in solid sate,respectively.Using CzAcSF as the host,the solution-processing OLEDs based on MTPA-BPSB achieved a maximum external quantum efficiency of 18.11%.(3)A novel donor unit 2,10'-diacridine was synthesized by molecular self-coupling reaction.Introduction of different acceptor groups,a series of D-A compounds based on 2,10'-diacridine derivatives were synthesized.These materials have good thermal stability because of their large rigid structure.All compounds show yellow-green luminescence in both solution and solid film.The compounds bearing sulfone and benzophenone units exhibit TADF properties,while the compounds with the acceptor structure of triazine shows common fluorescence.Obviously,the different acceptor units have great influence on the photophysical properties of materials.