Design,Synthesis And Characterization Of Novel Thermally Activated Delayed Fluorescence Emitters With Specific Conformations

This thesis focused on exploiting thermally activated delayed fluorescence(TADF)mechanism and a series of highly efficient TADF emitters were developed.Moreover,the effects of molecular conformations on their physical and electroluminescence properties were studied systematically.The important breakthroughs have been made as listed below:(1)To develop high-performance orange to red TADF emitters,it is urgent to develop novel molecular designing strategies ensuring small singlet-triplet energy splitting(ΔEST)and high radiation decay constant(kf)simultaneously.Herein two novel TADF emitters,named as 3-(4-(9,9-dimethyl-4-phenylacridin-10(9H)-yl)phenyl)-9H-thioxanthen-10,10-dioxide(TXO-PhDMAC),2-(4-(9,9-dimethyl-4-phenylacridin-10(9H)-yl)phenyl)anthracene-9,10-dione(AQ-PhDMAC)are developed by employing 9,9-dimethyl-4-phenyl-9,10-dihydroacridine(α-PhDMAC)with large steric hindrance as the donor segment.Owing to the steric effect of the extra α-phenyl group in α-PhDMAC,TXO-PhDMAC and AQ-PhDMAC both depict nearly planar conformations,which not only favor the high kf as well as small ΔEST,but also effectively restrict intermolecular interactions and relieve the annoying concentration quenching.Further applying TXO-PhDMAC and AQ-PhDMAC into OLEDs,they exhibit maximum external quantum efficiencies(EQEs)of 22.6%and 18.4%respectively.(2)A pair of novel chiral donors named as(R/S)-9-methyl-2,9-diphenyl-9,10-dihydroacridine(PMAc)are developed,which can be used for general TADF molecular design.Based on them,a pair of enantiomers(R/S)-TTR-PMAc with dual stable conformations are developed.Introducing chirality cannot influence conformational distributions in ground state,and thus(R/S)-TTR-PMAc show similar physical properties under conventional non-polarized conditions.While under chiroptical environments,they exhibit obvious mirror-like properties under circular dichroism(CD)and circularly polarized luminescence(CPL)measurement.In particular,in different aggrageted states,the different conformations of the enantiomers make different contributions to the photoluminescence properties,and thus they show different CPL properties in different aggragated states.Therefore,we further confirm that the chiroptical performances are influenced by different conformations.