| Circularly polarized organic liAghtb-esmtitrtiangc tdiodes(CP-OLEDs)have received increasing attention due to its potential application in 3D display,field-effect transistor devices for CP light detection,and point-of-care personalized diagnostic tools.The materials that have been reported for the preparation of CP-OLEDs include chiral polymer fluorescent materials,organometallic complexes,organic small molecule dyes and TADF materials.Devices from chiral polymer fluorescent materials generally have high circularly polarized electroluminescence asymmetry factors(g EL),but the performance(brightness and efficiency)of the devices is low.The device based on organometallic complexes and organic TADF materials can achieve excellent performance,while showed g EL values from 10-5 to 10-3.Up to date,the CP-OLEDs devices embrace simultaneously large g EL values and outstanding performance,which are still challenging technological barriers for practical applications.The circularly polarized electroluminescence asymmetry factor(g EL)is one of the important measurements for excellence or worseness of CP-OLEDs performance.Therefore,how to improve the g EL value has become one of the vital research contents of CP-OLEDs devices in currently.The luminophores were modified onto the chiral molecular skeleton or chiral small molecules were doped in liquid crystal polymer materials to obtain induced chirality,which can emit efficiently CP light.The disadvantage for point chiral molecules with unstable or only a single configuration.Planar chirality molecules(including chiral helicene and[2.2]paracyclophane)have difficulty in molecular structures modification with functionalized groups.Axial chiral molecules have stable chiral configuration and well chirality induction.Optical 1,1'-binaphthol(BINOL)is one of the representative axial chiral molecules,and its molecular structure can be modified easily.BINOL and its derivatives have been applied widely in circularly polarized luminescence(CPL)liquid crystal fluorescent dyes,CPL sensors and energy transfer gel CPL materials.There are few research reports on the application of binaphthyl derivatives in CP-OLEDs.The luminophores modification sites on BINOL skeleton,structure changes for these modified groups,and the dihedral angle values change for the binaphthyl unit have significant effects on the CPL properties of BINOL derivatives.However,there are few research reports on the application of binaphthyl derivatives in CP-OLEDs.In this dissertation,we firstly used groups with aggregated induced emission(AIE)effects as modified units on 3,3'-position of binaphthol skeleton,which increased the g EL value of their CP-OLEDs device by improving the luminescence performance of these CPL materials in aggregate state.Due to the highly distorted molecular structure of AIE luminophores,the entire CPL molecular structure is highly twisted,which is not conducive to form regular?-?stacking structure in solid films.Therefore,the|g EL|value of the device is only 3.2×10-3.Subsequently,the planar pyrene group was used to modify the 3,3'-position or 6,6'-position on binaphthol skeleton.It was found that the luminophore modification sites show significant effect on the CPL performance of these emitters.The CP-OLEDs device from 3,3'-position functionalized binaphthyl emitter with a larger|g EL|value.Next,by inserting various bridged alkyl chains into the hydroxyl groups of BINOL(dihedral angle),or introducing functionalized substituents with different steric hindrance on 3,3'-position of 2,2'-methylenedioxy-1,1'-binaphthalene(substituent effect),the dihedral angle value-and substituent-dependent CPL behaviours were systematically explored.In order to prepare the CP-OLEDs device with high brightness and g EL values,achiral light-emitting polymers were induced to obtain chirality by using binaphthyl derivatives as inducers.Finally,the structural change effect for achiral light-emitting polymer on their CPL performance induced by binaphthyl derivative was studied.The main works are as follows:1.Circularly polarized electroluminescence performance for chiral binaphthyl derivatives modified by AIE groupsIn this chapter,we prepared AIE-active CPL materials by modifying the binaphthol skeleton with AIE-active fluorescent groups,and explored its CP-OLEDs performance.A pair of AIE-active chiral binaphthyl derivatives(R/S)-2-6 were synthesized,by introducing tetrastyrene derivatives fluorophore into binaphthyl skeleton.The solid films of AIE-active emitters(R/S)-2-6 showed stable CPL signals,maximum|gem|=3.6×10-3,and high fluorescent quantum yield of 39.8%.The CP-OLEDs devices based on(R/S)-2-6 achieved turn-on voltages(Von),maximum brightness(Lmax),maximum current efficiency(CEmax),and maximum|g EL|values of3.18 V/3.24 V,8061 cd/m2/7946 cd/m2,1.32 cd/A/1.26 cd/A,and 3.2×10-3,respectively.The g EL values of(R/S)-2-6 are still in the order of 10-3,which may be ascribed to the distorted steric structure of tetrastyrene groups.After modifying tetrastyrene group on binaphthyl skeleton,the molecular structures of(R/S)-2-6 are highly distorted,which is prone to the irregular?-?stacking in the aggregation state and hinders its CPL performance.2.Circularly polarized electroluminescence performance for chiral binaphthyl derivatives modified by pyrene groupsIn this chapter,we studied the effect of fluorophore modification sites changes on the binaphthyl skeleton for its CPL performance.Two pairs of binaphthyl-pyrene enantiomers(R/S)-3-5 and(R/S)-3-6 were synthesized,by introducing pyrene units at3,3'-position or 6,6'-position on binaphthyl skeleton.The enantiomers(R/S)-3-5 and(R/S)-3-6 showed well carrier transport ability,arising from pyrene groups with very excellent carrier mobility.The compounds(R/S)-3-6 and(R/S)-3-5 in solid films obtained maximum|gem|values were 1.1×10-3 and 6.2×10-3,respectively.The|gem|value of(R/S)-3-5 is 5.6 times larger than that of(R/S)-3-6.Theoretical calculation results showed that only one thermodynamically stable groundstate geometries(S0)structure was obtained for(S)-3-6,but two optimized conformers(S)-3-6a(gem=-2.8×10-3)and(S)-3-6b(gem=+1.6×10-3)can be obtained in the first excited-state(S1).The entaniomers(R/S)-3-6 with free rotation conformation structure and large steric hindrance,the binaphthyl axis and pyrene groups can rotate freely,which is prone to the irregular?-?stacking in the aggregation state and hinders its CPL performance.In addition,conformers(S)-3-6a and(S)-3-6b with opposite sign could lead to a small gemvalue in experiment measurements.The calculated results also showed that for(S)-3-5,only one stable structure was observed both in S0and S1 state,the calculated gem value is-1.0×10-3(S1 state).Therefore,the exclusively stable geometrical structure both in S0 and S1 is one vital reason for(S)-3-5 to show strong CPL signals.The pyrene-functionalized entaniomers(R/S)-3-5 with planar rigid conjugated structures and stable molecular configurations,which is prone to the regular?-?stacking in the aggregation state and beneficial for its CPL performance.The enantiomers(R/S)-3-5-based devices achieved Von,Lmax,CEmax,and maximum|g EL|values of 3.43V/3.18 V,10886 cd/m2/11336 cd/m2,3.91 cd/A/3.86 cd/A,and 5.6×10-3,respectively.Modification planar rigid conjugated fluorophore at 3,3'-position of binaphthyl skeleton is conducive to its CPL performance.3.Circularly polarized electroluminescence performance for achiral polymer induced by binaphthyl derivativesIn this chapter,we studied the effect of molecular structure(the dihedral angles(?)between two naphthyl rings of the BINOL group and modifying fluorophores changes(on 3,3'-position substituent effects))for chiral binaphthyl derivatives on their CPL performance.Subsequently,the binaphthyl derivatives were used as chiral inducers to explore its effects on the chiral induction for achiral fluorescent polymer F8BT.By inserting various bridged alkyl chains(C1?C4)into the hydroxyl groups of BINOL,and modifying phenylcarbazole,triphenylamine,phenyl phenoxazine and pyrene on binaphthyl 3,3'-position,a series of binaphthyl derivatives((R/S)-4-1?(R/S)-4-10)were obtained.As the bridged alkyl chain length increases(C1?C4),the?values of enantiomers(R/S)-4-1?(R/S)-4-5 increases(?=50.01?104.46°),the molecular structures became more distorted,and its|gem|values and chirality induction to F8BT decreases.There were no significant?value changes were obsereved for entaniomers(R/S)-4-6?(R/S)-4-10 with methylene bridged the hydroxy group and 3,3'-position modified different groups on binaphthyl skeleton(?=50.01?52.73°).The CPL performance and chirality induction for binaphthyl derivatives modified with structurally distorted fluorophores on 3,3'-position were inferior.The binaphthyl derivatives((R/S)-4-1,(R/S)-4-6,(R/S)-4-9,and(R/S)-4-10)having small?values and planar rigid conjugated structures(?=50.01?52.38°)showed superior CPL luminescence performance and high chiral induction.The planar rigid conjugated structure of binaphthyl derivative(dihedral angles values)play a key role in improving its CPL performance.In order to obtain CP-OLEDs devices with high brightness and amplified|g EL|values,the blends from(R/S)-4-10and achiral light-emitting polymer F8BT were used as emitters.The CP-OLEDs devices based on F8BT and pyrene-functionalized chiral inducers(4-R/S-10)achieved Von,Lmax,CEmax,and maximum|g EL|values of 4.1 V,20572.6 cd/m2/21797.8 cd/m2,4.19/4.06 cd/A,and 9.8×10-3,respectively.Binaphthyl derivatives with rigid conjugated planar structure and strong intermolecular?-?interaction,can significantly enhance the interchain interaction of polymers,promote supermolecular self-assembly of F8BT in doped films.Amplified CPL signals could be obtained from achiral polymer F8BT induced by binaphthyl derivatives4.Circularly polarized electroluminescence performance for achiral polyfluorene derivatives induced by binaphthyl inducersIn this chapter,we introduced different molar ratios(1%,5%and 10%)chromophores(DMTRZ)into the achiral polyfluorene framework to improve its fluorescent performance.The effect of the molar ratio changes of DMTRZ unit on polymers chiral induced ability was also studied.Three achiral polymers P1,P2,and P3 were synthesized by introducing different molar ratio(1%,5%,and 10%)of DMTRZ groups to polyfluorene skeletons.As the DMTRZ groups molar ratio increase in polymers(P1?P3),the fluorescence quantum yield of polymers is enhanced,but the induced CPL signals are decreased.However,as the proportion of DMTRZ group increases,the steric hindrance is increased and the inter-chain interaction of polymers weaken,the chirality-induced self-assembly ability of polymers decreases.Since P3 has the best fluorescent performance,P3 was used as the emitter for electroluminescence properties research in subsequently.The CP-OLEDs based on the blends of P3 doped and 25 wt%chiral inducers(R/S)-4-6obtained Von,Lmax,CEmax,and maximum|g EL|values of 4.8 V,10287 cd/m2/10693cd/m2,4.25 cd/A/4.06 cd/A,and 1.7×10-2,respectively.Introducing DMTRZ group with distorted molecular structure into polyfluorene skeletons can significantly improve its fluorescent performance.This result can provide a valuable reference for future dopant-induced CP-OLEDs device design. |
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