Chirality is an important natural characteristic of organic molecules,and chiral organic molecules have shown extensive application in areas such as pharmaceutical development and material science.Benefiting from the ...Chirality is an important natural characteristic of organic molecules,and chiral organic molecules have shown extensive application in areas such as pharmaceutical development and material science.Benefiting from the ability to achieve circularly polarized luminescence(CPL),chiral luminescent materials have shown potential applications in anti-glare display,optical communication and,3D display,etc.Due to the ability to harvest both singlet and triplet excitons by a fast reverse intersystem crossing process without involving noble metals,chiral thermally activated delayed fluorescence(TADF)materials with point chirality,axial chirality,planar chirality and helical chirality are regarded as the state-of-the-art materials for circularly polarized organic light-emitting diodes(CP-OLEDs).In recent years,the chiral TADF materials and CP-OLEDs have rapidly developed,but unfortunately,the dissymmetry factors(g)are far from the requirement of practical applications.The ideal emitters and devices should have both high efficiency and a g factor,or at least a balance between these two elements.This review gives an overview of recent progress in chiral TADF materials,with a particular focus on the chiral skeleton,CPL property and device performance.Furthermore,the molecular design concept,device structure and methods to improve the g factors of chiral materials and CP-OLEDs are also discussed.展开更多
Helicene-based emitters with unique inherent circularly polarized luminescence(CPL)are promising yet remain a formidable challenge for highly efficient circularly polarized organic light-emitting diodes(CP-OLEDs),ascr...Helicene-based emitters with unique inherent circularly polarized luminescence(CPL)are promising yet remain a formidable challenge for highly efficient circularly polarized organic light-emitting diodes(CP-OLEDs),ascribed to their tough synthesis,low emission efficiency,and easy racemization in the thermal deposition process.Herein,a pair of helicenebased enantiomers,namely(P)-helicene-BN and(M)-helicene-BN,were developed,which merge helical chirality and the B/N/S inserted polycyclic aromatic framework to concurrently feature CPL and narrow thermally activated delayed fluorescence(TADF)characteristics.Benefiting from the excellent thermal/photophysical/chiroptical properties,the narrowband green CP-OLEDs based on enantiomers achieved maximum external quantum efficiencies(EQE_(max))of up to 31.5%,and dissymmetry factor(|g_(EL)|)of 2.2×10^(−3).This work reveals the great potential of helicene-based emitters in CP-OLEDs.展开更多
Circularly polarized organic light-emitting diode(CP-OLED) has attracted increasing interest for its efficient ability to generate circularly polarized light directly. So far, many CP-OLEDs were successfully fabricate...Circularly polarized organic light-emitting diode(CP-OLED) has attracted increasing interest for its efficient ability to generate circularly polarized light directly. So far, many CP-OLEDs were successfully fabricated with chiral emitters or chiral hosts. In this study, a new strategy based on chiral electron transporting layer is proposed to construct CP-OLEDs. A pair of chiral electron transporting materials, 1,3,5-tris((R/S)-4-isopropyl-4,5-dihydrooxazol-2-yl)benzene((R/S)-TOx^(i)Pr), are firstly designed and synthesized. The crystalline films of(R/S)-TOx^(i)Pr show circularly polarized photoluminescence with photoluminescence dissymmetry factors of-0.067 and +0.041, respectively. The CP-OLEDs based on(R/S)-TOx^(i)Pr and three types of achiral emitters all exhibit circularly polarized electroluminescence, showing feasibility and strong versatility of this new strategy. The mechanism is attributed to in-situ electrical excitation instead of simply light filtering of non-circularly polarized light. This work demonstrates a new approach for realizing circularly polarized electroluminescence which may provide a valuable strategy to develop CP-OLEDs.展开更多
This study optimized the TADF feature of axial chiral enantiomers through precise donor engineering,and multicolor CP-TADFwas achieved in the axial chiral framework.Three pairs of axial enantiomers with donor-regulate...This study optimized the TADF feature of axial chiral enantiomers through precise donor engineering,and multicolor CP-TADFwas achieved in the axial chiral framework.Three pairs of axial enantiomers with donor-regulated TADF feature,namely(R/S)-TPCBD,(R/S)-DPCBD,and(R/S)-DPACBD,were synthesized by introducing carbazole donors with different substituents onto biphenyl cyanide acceptors.As the electron-donating ability of donors increases,the emission of these axial enantiomers ranges from 455,476 to 552 nm,their singlet-triplet energy gaps(ΔE_(ST))gradually decrease from 0.30,0.22 to 0.02 e V,accompanied by an increasement in the transition rate(k_(RISC))of RISC process,and the k_(RISC)of DPACBD could reach up to 7.16×10^(5)s^(-1).These axial enantiomers also exhibit mirror-image CD and circularly polarized luminescence(CPL)properties.Moreover,OLEDs based on TPCBD,DPCBD,and DPACBD as emitter were then fabricated,which displayed blue,green,and orange electroluminescence with EQE_(max)of 13.0%,16.4%,and 25.0%,respectively.The results also exhibited a phenomenon of device efficiency increasing with the enhancement of donor abilities.Notably,the CP-OLEDs using(R/S)-TPCBD,(R/S)-DPCBD and(R/S)-DPACBD as emitters displayed intense CPEL signals with g_(EL)values of 3.4×10^(-3)/-4.1×10^(-3),3.2×10^(-3)/-3.1×10^(-3)and2.3×10^(-3)/-2.1×10^(-3),respectively.By convenient molecular engineering of donor regulation in the same molecular skeleton,CP-TADF materials with multicolor CPEL and improved device performance could be conveniently achieved.展开更多
D-A charge transfer, including through-bond charge transfer and through-space charge transfer between two different electron donors(D) and electron acceptors(A), is a fundamental and powerful tool to tune the optical ...D-A charge transfer, including through-bond charge transfer and through-space charge transfer between two different electron donors(D) and electron acceptors(A), is a fundamental and powerful tool to tune the optical properties of organic dyes. Herein,we demonstrate a unique strategy to tune phosphorescence and circularly polarized luminescence properties of axially chiral binuclear Pt(Ⅱ) complexes through long-range charge transfer, even though these molecules have two totally identical segments on either side of the chiral core. The presence of axial chirality would break not only the symmetry of molecular structure and π-conjugation system but also the symmetry of charge distribution for long-range charge transfer. These binaphthyl-based Pt(Ⅱ)complexes bearing coordinated atoms far away from chiral axis exhibit no Pt-Pt interactions but colorful concentrationdependent phosphorescence with quantum yield up to 86.4% and could be applied as emitters in highly efficient solutionprocessed organic light-emitting diodes to achieve luminance, luminance efficiency, power efficiency, external quantum efficiency, and asymmetry factor up to 8.94 × 10^(3)cd m^(-2), 41.9 cd A-1, 18.8 lm W^(-1), 12.6% and 2.98 × 10^(-3), respectively. Therefore,the present work affords a new and simple way to utilize the inherently asymmetric advantage of chirality for the design of D-Abased organic dyes.展开更多
Chiral organometallic emitters hold great promise in potential and practical applications of circularly polarized organic lightemitting diodes(CP-OLEDs).However,developing luminescent earth-abundant organometallic com...Chiral organometallic emitters hold great promise in potential and practical applications of circularly polarized organic lightemitting diodes(CP-OLEDs).However,developing luminescent earth-abundant organometallic complexes concurrently exhibiting circularly polarized luminescence(CPL)and high quantum efficiency remains a formidable challenge.In this study,we introduced a typical planar chiral skeleton of a[2.2]paracyclophane moiety into earth-abundant copper(I)complexes with the goal of realizing efficient CPL and thermally activated delayed fluorescence(TADF)simultaneously.Two pairs of proof-of-theconcept copper(I)enantiomers,R_(p)/S_(p)-MAC^(*)-Cu-CzP and R_(p)/S_(p)-MAC^(*)-Cu-CNCzP,were developed using planar chiral[2.2]paracyclophane-based donor ligands in a carbene-metal-amide(CMA)motif.Both panels of enantiomers not only exhibited significant mirror-image CPL signals but also displayed distinct TADF nature with fast reverse intersystem crossing rates of up to 10^(8)s^(-1).The resultant OLEDs based on the MAC^(*)-Cu-Cz P enantiomers manifested efficient circularly polarized electroluminescence with excellent external quantum efficiencies of 13.2%and ultraslow efficiency roll-off(7.7%at 10,000 nits).This article not only demonstrates one of the best performances for CP-OLEDs based on earth-abundant organometallic complexes but also represents the first example of CP-OLEDs from CMA complexes to our knowledge.展开更多
Realizing both a high emission efficiency and luminescence dissymmetry factor(g_(lum))in circularly polarized solution processable organic light-emitting diodes(CP-OLEDs)remains a significant challenge.In this contrib...Realizing both a high emission efficiency and luminescence dissymmetry factor(g_(lum))in circularly polarized solution processable organic light-emitting diodes(CP-OLEDs)remains a significant challenge.In this contribution,two chiral phosphorescent liquid crystals based on cyclometalated platinum complexes are prepared,in which the chiral s-2-methyl-1-butyl group is introduced into the cyclometalating ligand and the mesogenic fragment is attached to the periphery of the ancillary ligand.The platinum complexes exhibit both smectic and chiral nematic phases as evidenced by polarized optical microscopy,differential scanning calorimetry and small-angle X-ray diffraction.Remarkably,a high photoluminescent quantum efficiency of over 78%and clear circularly polarized luminescent signal with g_(PL)of about 10^(-2)are observed for the complexes.Further,solution-processed CP-OLEDs show maximum external quantum efficiencies(EQE)of over 15%and strong circularly polarized electroluminescent signals with a g_(EL)≈10^(-2).This research demonstrates that both liquid crystallinity and the number of chiral centers play key roles in improving the chiroptical property,paving the way for a new approach for the design of high-efficiency CPL emitters.展开更多
The research in circularly polarized luminescence has attracted wide interest in recent years.Efforts on one side are directed toward the development of chiral materials with both high luminescence efficiency and diss...The research in circularly polarized luminescence has attracted wide interest in recent years.Efforts on one side are directed toward the development of chiral materials with both high luminescence efficiency and dissymmetry factors,and on the other side,are focused on the exploitations of these materials in optoelectronic applications.This review summarizes the recent frontiers(mostly within five years)in the research in circularly polarized luminescence,including the development of chiral emissive materials based on organic small molecules,compounds with aggregation-induced emissions,supramolecular assemblies,liquid crystals and liquids,polymers,metal-ligand coordination complexes and assemblies,metal clusters,inorganic nanomaterials,and photon upconversion systems.In addition,recent applications of related materials in organic light-emitting devices,circularly polarized light detectors,and organic lasers and displays are also discussed.展开更多
A new strategy of thermally activated delayed fluorescence(TADF)material-sensitized circularly polarized luminescence(CPL)has been proposed for improving the efficiencies of fluorescent circularly polarized organic li...A new strategy of thermally activated delayed fluorescence(TADF)material-sensitized circularly polarized luminescence(CPL)has been proposed for improving the efficiencies of fluorescent circularly polarized organic lightemitting diodes(OLEDs)(CP-OLEDs).Consequently,a pair of helicene enantiomers,(P)-HAI and(M)-HAI,were synthesized.The helicene enantiomers with the rigid helicalπ-skeleton had highly thermal and enantiomeric stabilities,and they also showed excellent photophysical properties,especially,intense mirror-image CPL activities with large luminescence dissymmetry factor(|g_(lum)|)values of about 6×10^(-3).Notably,the CP-OLEDs with the helicene enantiomers as emitters and a TADF molecule as sensitizer not only displayed better performance of lower turn-on voltage(V_(T))of 2.6 V,four-fold maxmium-external quantum efficiency(EQE_(max))of 5.3%,and lower efficiencies roll-off of 1.9%at 1000 cd m^(-2),than those of the devices without TADF sensitizer,but also exhibited intense circularly polarized electroluminescence(CPEL)with the electroluminescence dissymmetry factor(g_(EL))values of-2.3×10^(-3)and+3.0×10^(-3).Meanwhile,this study also represents the first thermally activated sensitized fluorescent CP-OLEDs with markedly enhanced efficiencies and intense CPEL.展开更多
An efficient strategy for constructing chiral macrocycles with both thermally activated delayed fluorescence(TADF)and highly efficient circularly polarized electroluminescence(CPEL)properties was developed.Consequentl...An efficient strategy for constructing chiral macrocycles with both thermally activated delayed fluorescence(TADF)and highly efficient circularly polarized electroluminescence(CPEL)properties was developed.Consequently,a pair of macrocyclic enantiomers(+)-(R,R)-MC and(−)-(S,S)-MC was synthesized by a combination of chiral octahydro-binaphthol moiety with triazine-based TADF skeleton.The chiral macrocycles exhibited obvious TADF properties with a lowΔE_(ST) of 0.067 eV,aggregation-induced emission behaviors,and high photoluminescence quantum yields of up to 79.7%.Moreover,the macrocyclic enantiomers showed mirror images in circular dichroism spectra and circularly polarized luminescence signals.Especially,the chiralmacrocycleswere suitable for the preparation of solution-processed circularly polarized organic light-emitting diodes,which displayed excellent device performances with a highmaximum external quantum efficiency of up to 17.1%,low-efficiency roll-off of 3.5%at 1000 cdm^(−2),andintenseCPELalong with electroluminescence dissymmetry factor of 1.7×10^(−3).展开更多
The simultaneous achievement of chiral multiple-resonance thermally activated delayed fluorescence(MR-TADF)emitters with narrowband and circularly polarized electroluminescence(CPEL)poses a challenge.Herein,a MR-TADF ...The simultaneous achievement of chiral multiple-resonance thermally activated delayed fluorescence(MR-TADF)emitters with narrowband and circularly polarized electroluminescence(CPEL)poses a challenge.Herein,a MR-TADF emitter,Spiro-BNCz,embedding spirofluorene structure was developed and chiral separated,whose emission peaks at 528 nm in toluene with Commission Internationale de L’Eclairage coordinates of(0.26,0.69).The conjugation extension caused by embedding sulfur substituted spirofluorene on B/N framework shortens the singlettriplet energy gap and increases spin-orbital coupling matrix element.Therefore,a fast reverse intersystem crossing rate constant of 2.8×10^(6)s^(−1)and a high photoluminescence efficiency of 92%in film were achieved.The organic light-emitting diode(OLED)exhibits a maximum external quantum efficiency of 32.3%.Particularly,the circularly polarized OLEDs based on Spiro-BNCz enantiomers show symmetric CPEL with dissymmetry factors(|gEL|)≈10^(−3).展开更多
The currently reported axial chiral molecules based on the 3,3'-substitution of the binaphthyl skeleton are limited by intrinsic fluorescence properties,resulting in generally low device efficiencies(EQE<5%)of ...The currently reported axial chiral molecules based on the 3,3'-substitution of the binaphthyl skeleton are limited by intrinsic fluorescence properties,resulting in generally low device efficiencies(EQE<5%)of related organic light emitting diodes(OLEDs).Herein,we designed and synthesized four pair of chiral binaphthyl enantiomers(R/S-1-R/S-4)adopting acceptor-donor-donor-acceptor(ADDA)structure by introducing different thioxanthone modification groups on the 3,3'-position of 2,2'-dimethoxy-1,1'-binaphthalene.Among them,emitter R/S-2 and R/S-4 obtained by enhancing intramolecular charge transfer exhibited TADF characteristics due to relatively small Est of 0.12eV and 0.17eV,and relatively moderate SOC matrix elements of 0.28 cm^(-1)and 0.10 cm^(-1)between the 1CT and 3LE states.The CD spectra of these enantiomers in diluted solutions showed perfect mirror images and reasonable gabs for small organic molecules(10^(-4)-10^(-3)).And the external quantum eficiencies(EQE)of 10.9%and 8.32%for device A and B based on emitter S-2 and S-4 were highest compared with currently reported axial chiral molecules based on the 3,3'-position substitution of binaphthyl skeleton,providing simple molecular design strategies to construct efficient CP-OLED device.展开更多
基金supported by the National Natural Science Foundation of China(92256304,U23A20593)the Fundamental Research Funds for the Central Universities(020514380294)。
文摘Chirality is an important natural characteristic of organic molecules,and chiral organic molecules have shown extensive application in areas such as pharmaceutical development and material science.Benefiting from the ability to achieve circularly polarized luminescence(CPL),chiral luminescent materials have shown potential applications in anti-glare display,optical communication and,3D display,etc.Due to the ability to harvest both singlet and triplet excitons by a fast reverse intersystem crossing process without involving noble metals,chiral thermally activated delayed fluorescence(TADF)materials with point chirality,axial chirality,planar chirality and helical chirality are regarded as the state-of-the-art materials for circularly polarized organic light-emitting diodes(CP-OLEDs).In recent years,the chiral TADF materials and CP-OLEDs have rapidly developed,but unfortunately,the dissymmetry factors(g)are far from the requirement of practical applications.The ideal emitters and devices should have both high efficiency and a g factor,or at least a balance between these two elements.This review gives an overview of recent progress in chiral TADF materials,with a particular focus on the chiral skeleton,CPL property and device performance.Furthermore,the molecular design concept,device structure and methods to improve the g factors of chiral materials and CP-OLEDs are also discussed.
基金This work was supported by the National Natural Science Foundation of China(grant nos.52130308,51903160,and 52022071)Shenzhen Science and Technology Program(grant no.KQTD20170330110107046)the Shenzhen Technology and Innovation Commission(grant no.JCYJ20180507182244027).
文摘Helicene-based emitters with unique inherent circularly polarized luminescence(CPL)are promising yet remain a formidable challenge for highly efficient circularly polarized organic light-emitting diodes(CP-OLEDs),ascribed to their tough synthesis,low emission efficiency,and easy racemization in the thermal deposition process.Herein,a pair of helicenebased enantiomers,namely(P)-helicene-BN and(M)-helicene-BN,were developed,which merge helical chirality and the B/N/S inserted polycyclic aromatic framework to concurrently feature CPL and narrow thermally activated delayed fluorescence(TADF)characteristics.Benefiting from the excellent thermal/photophysical/chiroptical properties,the narrowband green CP-OLEDs based on enantiomers achieved maximum external quantum efficiencies(EQE_(max))of up to 31.5%,and dissymmetry factor(|g_(EL)|)of 2.2×10^(−3).This work reveals the great potential of helicene-based emitters in CP-OLEDs.
基金supported by the National Natural Science Foundation of China (92156016, U23A20593 and 22071003)the National Key R&D Program of China (2021YFB3500400, 2021YFB3501800 and 2022YFB3503700)the China Postdoctoral Science Foundation (2023TQ0004)。
文摘Circularly polarized organic light-emitting diode(CP-OLED) has attracted increasing interest for its efficient ability to generate circularly polarized light directly. So far, many CP-OLEDs were successfully fabricated with chiral emitters or chiral hosts. In this study, a new strategy based on chiral electron transporting layer is proposed to construct CP-OLEDs. A pair of chiral electron transporting materials, 1,3,5-tris((R/S)-4-isopropyl-4,5-dihydrooxazol-2-yl)benzene((R/S)-TOx^(i)Pr), are firstly designed and synthesized. The crystalline films of(R/S)-TOx^(i)Pr show circularly polarized photoluminescence with photoluminescence dissymmetry factors of-0.067 and +0.041, respectively. The CP-OLEDs based on(R/S)-TOx^(i)Pr and three types of achiral emitters all exhibit circularly polarized electroluminescence, showing feasibility and strong versatility of this new strategy. The mechanism is attributed to in-situ electrical excitation instead of simply light filtering of non-circularly polarized light. This work demonstrates a new approach for realizing circularly polarized electroluminescence which may provide a valuable strategy to develop CP-OLEDs.
基金supported by the National Natural Science Foundation of China(22122111,92256304)the Ministry of Science and Technology of China(2022YFA1204401)。
文摘This study optimized the TADF feature of axial chiral enantiomers through precise donor engineering,and multicolor CP-TADFwas achieved in the axial chiral framework.Three pairs of axial enantiomers with donor-regulated TADF feature,namely(R/S)-TPCBD,(R/S)-DPCBD,and(R/S)-DPACBD,were synthesized by introducing carbazole donors with different substituents onto biphenyl cyanide acceptors.As the electron-donating ability of donors increases,the emission of these axial enantiomers ranges from 455,476 to 552 nm,their singlet-triplet energy gaps(ΔE_(ST))gradually decrease from 0.30,0.22 to 0.02 e V,accompanied by an increasement in the transition rate(k_(RISC))of RISC process,and the k_(RISC)of DPACBD could reach up to 7.16×10^(5)s^(-1).These axial enantiomers also exhibit mirror-image CD and circularly polarized luminescence(CPL)properties.Moreover,OLEDs based on TPCBD,DPCBD,and DPACBD as emitter were then fabricated,which displayed blue,green,and orange electroluminescence with EQE_(max)of 13.0%,16.4%,and 25.0%,respectively.The results also exhibited a phenomenon of device efficiency increasing with the enhancement of donor abilities.Notably,the CP-OLEDs using(R/S)-TPCBD,(R/S)-DPCBD and(R/S)-DPACBD as emitters displayed intense CPEL signals with g_(EL)values of 3.4×10^(-3)/-4.1×10^(-3),3.2×10^(-3)/-3.1×10^(-3)and2.3×10^(-3)/-2.1×10^(-3),respectively.By convenient molecular engineering of donor regulation in the same molecular skeleton,CP-TADF materials with multicolor CPEL and improved device performance could be conveniently achieved.
基金supported by the National Natural Science Foundation of China (21871192)the Major Program of Guangdong Basic and Applied Research (2019B030302009)。
文摘D-A charge transfer, including through-bond charge transfer and through-space charge transfer between two different electron donors(D) and electron acceptors(A), is a fundamental and powerful tool to tune the optical properties of organic dyes. Herein,we demonstrate a unique strategy to tune phosphorescence and circularly polarized luminescence properties of axially chiral binuclear Pt(Ⅱ) complexes through long-range charge transfer, even though these molecules have two totally identical segments on either side of the chiral core. The presence of axial chirality would break not only the symmetry of molecular structure and π-conjugation system but also the symmetry of charge distribution for long-range charge transfer. These binaphthyl-based Pt(Ⅱ)complexes bearing coordinated atoms far away from chiral axis exhibit no Pt-Pt interactions but colorful concentrationdependent phosphorescence with quantum yield up to 86.4% and could be applied as emitters in highly efficient solutionprocessed organic light-emitting diodes to achieve luminance, luminance efficiency, power efficiency, external quantum efficiency, and asymmetry factor up to 8.94 × 10^(3)cd m^(-2), 41.9 cd A-1, 18.8 lm W^(-1), 12.6% and 2.98 × 10^(-3), respectively. Therefore,the present work affords a new and simple way to utilize the inherently asymmetric advantage of chirality for the design of D-Abased organic dyes.
基金financial support from the National Natural Science Foundation of China(52022071 and 51873158)。
文摘Chiral organometallic emitters hold great promise in potential and practical applications of circularly polarized organic lightemitting diodes(CP-OLEDs).However,developing luminescent earth-abundant organometallic complexes concurrently exhibiting circularly polarized luminescence(CPL)and high quantum efficiency remains a formidable challenge.In this study,we introduced a typical planar chiral skeleton of a[2.2]paracyclophane moiety into earth-abundant copper(I)complexes with the goal of realizing efficient CPL and thermally activated delayed fluorescence(TADF)simultaneously.Two pairs of proof-of-theconcept copper(I)enantiomers,R_(p)/S_(p)-MAC^(*)-Cu-CzP and R_(p)/S_(p)-MAC^(*)-Cu-CNCzP,were developed using planar chiral[2.2]paracyclophane-based donor ligands in a carbene-metal-amide(CMA)motif.Both panels of enantiomers not only exhibited significant mirror-image CPL signals but also displayed distinct TADF nature with fast reverse intersystem crossing rates of up to 10^(8)s^(-1).The resultant OLEDs based on the MAC^(*)-Cu-Cz P enantiomers manifested efficient circularly polarized electroluminescence with excellent external quantum efficiencies of 13.2%and ultraslow efficiency roll-off(7.7%at 10,000 nits).This article not only demonstrates one of the best performances for CP-OLEDs based on earth-abundant organometallic complexes but also represents the first example of CP-OLEDs from CMA complexes to our knowledge.
基金from the National Natural Science Foundation of China(Nos.51773021,51911530197,51473140)the Royal Society(IEC/NSFC/181139)+3 种基金the National Natural Science Foundation of China(Nos.51911530197 and 51773021)for an International Exchange Award(D.W.Bruce and Y.Wang)Six Talent Peaks Project in Jiangsu Province(No.XCL-102)Natural Science Fund for Colleges and Universities in Jiangsu Province(No.19KJA430002)Key technological tasks in Anhui Province(No.JB20007)。
文摘Realizing both a high emission efficiency and luminescence dissymmetry factor(g_(lum))in circularly polarized solution processable organic light-emitting diodes(CP-OLEDs)remains a significant challenge.In this contribution,two chiral phosphorescent liquid crystals based on cyclometalated platinum complexes are prepared,in which the chiral s-2-methyl-1-butyl group is introduced into the cyclometalating ligand and the mesogenic fragment is attached to the periphery of the ancillary ligand.The platinum complexes exhibit both smectic and chiral nematic phases as evidenced by polarized optical microscopy,differential scanning calorimetry and small-angle X-ray diffraction.Remarkably,a high photoluminescent quantum efficiency of over 78%and clear circularly polarized luminescent signal with g_(PL)of about 10^(-2)are observed for the complexes.Further,solution-processed CP-OLEDs show maximum external quantum efficiencies(EQE)of over 15%and strong circularly polarized electroluminescent signals with a g_(EL)≈10^(-2).This research demonstrates that both liquid crystallinity and the number of chiral centers play key roles in improving the chiroptical property,paving the way for a new approach for the design of high-efficiency CPL emitters.
基金financially supported by the National Natural Science Foundation of China(21925112,22090021,21890734,21975118,51973011,52003022,91956119,92061201,21825106,91856115,21874058,21771114,91956130)the Research Grants Council of Hong Kong(C6014-20W)the Innovation and Technology Commission(ITC-CNERC14SC01)。
文摘The research in circularly polarized luminescence has attracted wide interest in recent years.Efforts on one side are directed toward the development of chiral materials with both high luminescence efficiency and dissymmetry factors,and on the other side,are focused on the exploitations of these materials in optoelectronic applications.This review summarizes the recent frontiers(mostly within five years)in the research in circularly polarized luminescence,including the development of chiral emissive materials based on organic small molecules,compounds with aggregation-induced emissions,supramolecular assemblies,liquid crystals and liquids,polymers,metal-ligand coordination complexes and assemblies,metal clusters,inorganic nanomaterials,and photon upconversion systems.In addition,recent applications of related materials in organic light-emitting devices,circularly polarized light detectors,and organic lasers and displays are also discussed.
基金the National Natural Science Foundation of China(21871272,91956119 and 21521002)the Youth Innovation Promotion Association CAS(2019034)Qingdao University of Science and Technology(QUSTHX201929)。
文摘A new strategy of thermally activated delayed fluorescence(TADF)material-sensitized circularly polarized luminescence(CPL)has been proposed for improving the efficiencies of fluorescent circularly polarized organic lightemitting diodes(OLEDs)(CP-OLEDs).Consequently,a pair of helicene enantiomers,(P)-HAI and(M)-HAI,were synthesized.The helicene enantiomers with the rigid helicalπ-skeleton had highly thermal and enantiomeric stabilities,and they also showed excellent photophysical properties,especially,intense mirror-image CPL activities with large luminescence dissymmetry factor(|g_(lum)|)values of about 6×10^(-3).Notably,the CP-OLEDs with the helicene enantiomers as emitters and a TADF molecule as sensitizer not only displayed better performance of lower turn-on voltage(V_(T))of 2.6 V,four-fold maxmium-external quantum efficiency(EQE_(max))of 5.3%,and lower efficiencies roll-off of 1.9%at 1000 cd m^(-2),than those of the devices without TADF sensitizer,but also exhibited intense circularly polarized electroluminescence(CPEL)with the electroluminescence dissymmetry factor(g_(EL))values of-2.3×10^(-3)and+3.0×10^(-3).Meanwhile,this study also represents the first thermally activated sensitized fluorescent CP-OLEDs with markedly enhanced efficiencies and intense CPEL.
基金This work was supported by the National Natural Science Foundation of China(nos.21971235,91956119,22122111,and 92056109)Beijing National Laboratory for Molecular Sciences(no.BNLMS-CXXM-202105)Youth Innovation Promotion Association CAS(no.2019034).
文摘An efficient strategy for constructing chiral macrocycles with both thermally activated delayed fluorescence(TADF)and highly efficient circularly polarized electroluminescence(CPEL)properties was developed.Consequently,a pair of macrocyclic enantiomers(+)-(R,R)-MC and(−)-(S,S)-MC was synthesized by a combination of chiral octahydro-binaphthol moiety with triazine-based TADF skeleton.The chiral macrocycles exhibited obvious TADF properties with a lowΔE_(ST) of 0.067 eV,aggregation-induced emission behaviors,and high photoluminescence quantum yields of up to 79.7%.Moreover,the macrocyclic enantiomers showed mirror images in circular dichroism spectra and circularly polarized luminescence signals.Especially,the chiralmacrocycleswere suitable for the preparation of solution-processed circularly polarized organic light-emitting diodes,which displayed excellent device performances with a highmaximum external quantum efficiency of up to 17.1%,low-efficiency roll-off of 3.5%at 1000 cdm^(−2),andintenseCPELalong with electroluminescence dissymmetry factor of 1.7×10^(−3).
基金National Natural Science Foundation of China,Grant/Award Numbers:92256304,21975119,22171092。
文摘The simultaneous achievement of chiral multiple-resonance thermally activated delayed fluorescence(MR-TADF)emitters with narrowband and circularly polarized electroluminescence(CPEL)poses a challenge.Herein,a MR-TADF emitter,Spiro-BNCz,embedding spirofluorene structure was developed and chiral separated,whose emission peaks at 528 nm in toluene with Commission Internationale de L’Eclairage coordinates of(0.26,0.69).The conjugation extension caused by embedding sulfur substituted spirofluorene on B/N framework shortens the singlettriplet energy gap and increases spin-orbital coupling matrix element.Therefore,a fast reverse intersystem crossing rate constant of 2.8×10^(6)s^(−1)and a high photoluminescence efficiency of 92%in film were achieved.The organic light-emitting diode(OLED)exhibits a maximum external quantum efficiency of 32.3%.Particularly,the circularly polarized OLEDs based on Spiro-BNCz enantiomers show symmetric CPEL with dissymmetry factors(|gEL|)≈10^(−3).
基金funded by National Natural Science Foundation of China(No.21772209)International Partnership Program of Chinese Academy of Sciences(IPP)(No.1A1111KYSB20210028)National Program for Support of Top-notch Young Professionals.
文摘The currently reported axial chiral molecules based on the 3,3'-substitution of the binaphthyl skeleton are limited by intrinsic fluorescence properties,resulting in generally low device efficiencies(EQE<5%)of related organic light emitting diodes(OLEDs).Herein,we designed and synthesized four pair of chiral binaphthyl enantiomers(R/S-1-R/S-4)adopting acceptor-donor-donor-acceptor(ADDA)structure by introducing different thioxanthone modification groups on the 3,3'-position of 2,2'-dimethoxy-1,1'-binaphthalene.Among them,emitter R/S-2 and R/S-4 obtained by enhancing intramolecular charge transfer exhibited TADF characteristics due to relatively small Est of 0.12eV and 0.17eV,and relatively moderate SOC matrix elements of 0.28 cm^(-1)and 0.10 cm^(-1)between the 1CT and 3LE states.The CD spectra of these enantiomers in diluted solutions showed perfect mirror images and reasonable gabs for small organic molecules(10^(-4)-10^(-3)).And the external quantum eficiencies(EQE)of 10.9%and 8.32%for device A and B based on emitter S-2 and S-4 were highest compared with currently reported axial chiral molecules based on the 3,3'-position substitution of binaphthyl skeleton,providing simple molecular design strategies to construct efficient CP-OLED device.
