Synthesis Of Novel Chiral Luminescence Molecules Based On Anthracene In OLEDs

As a new generation of organic light-emitting diode(OLED)pure organic light-emitting material,thermally activated delayed fluorescence(TADF)material has a small single state(S₁)-three state(T₁)energy level difference(?E_ST<0.3e V),which can make 75%of triplet excitons pass through the antisystem to singlet for delayed luminescence,and its internal quantum efficiency can reach 100%in theory.In recent years,it has attracted extensive attention in scientific research and industrial fields at home and abroad.However,efficient TADF molecules need both small?E_ST and large singlet radiation transition rate,which are theoretically contradictory to each other.Therefore,recently,people have developed thermally activated sensitized luminescence mechanism,using TADF molecule as the main material to improve the utilization rate of excitons,and traditional fluorescent/phosphorescent materials as the luminescent object,realizing the construction of efficient OLED.Similar to the development of OLED,the electrocircularly polarized light-emitting diodes(CP-OLED),which can directly obtain circularly polarized light,also undergo three phases of chiral fluorescent materials,chiral phosphorescent materials,and chiral TADF materials.However,chiral TADF materials are a class of"super molecules"with high quantum yield,TADF,strong circular polarization luminescence(CPL),good mobility and many other properties,which greatly increases the design and synthesis difficulty.In this paper,a pair of chiral fluorescent molecules with high fluorescence quantum yield(PLQY)were designed and synthesized,which were used as the luminescence object and TADF molecule as the sensitization subject.By using thermally activated sensitization mechanism,a CP-OLED with high device efficiency was constructed.The main contents and results include:Based on the characteristics of high PLQY in anthracene derivatives,we introduce the chiral group-octahydrobinaphthols(OBN)into the framework of anthracene,and then introduce the aromatic amine group to improve the molecular solubility and PLQY,and finally obtain a pair of chiral fluorescence enantiomers with high PLQY.Starting from the commercial raw material difluoro-phthalic anhydride,tetrafluoro-substituted anthraquinone was obtained by Fourier reaction.Then,chiral OBN was inserted into the framework of anthraquinone by nucleophilic substitution reaction to obtain chiral anthraquinone.Then,the chiral fluorescent molecules((+)-(R,R)-OBN-PAD and(-)-(S,S)-OBN-PAD)based on anthraquinone were obtained by three steps of reaction,namely reduction reaction,bromatization reaction and palladium catalytic carbon-nitrogen coupling reaction.Subsequently,we characterized the structure and purity of the new molecule by means of NMR,high resolution mass spectrometry,elemental analysis,HPLC,and single crystal analysis,which provided a material basis for exploring its photoelectric properties.Then we characterized the photoelectric properties in detail.The fluorescence emission peak of the chiral fluorescence molecule in toluene is 526 nm,PLQY is up to 98%,and the molecule also has significant properties of CD and CPL.The asymmetry factor(g_lum)is 2.1×10^-3 and-2.4×10^-3.Using Ph Cz Trz as the wide-energy-gap host,TADF material PXZ-DPS as sensitizer,(+)-(R,R)-OBN-PAD and(-)-(S,S)-OBN-PAD was used as the three-way luminescent layer to prepare CP-OLED device.After device screening and optimization,the optimal ratio of the three luminescent layers was 1:10%:1%.The resulting CP-OLED EQE_max was21.3%,the starting voltage was 3.0V,and the device also had very low efficiency roll-off.At the same time,the obtained devices also have obvious properties of circularly polarized electroluminescence,and the asymmetry factor(g _EL)are+1.8×10^-3 and-1.4×10^-3,which provides a new strategy for the preparation of high efficiency,energy saving and stable CP-OLED.