Aggregation-induced thermally activated delayed fluorescence(TADF)phenomena have attracted extensive attention recently.In this paper,several theoretical models including monomer,dimer,and complex are used for the exp...Aggregation-induced thermally activated delayed fluorescence(TADF)phenomena have attracted extensive attention recently.In this paper,several theoretical models including monomer,dimer,and complex are used for the explanation of the luminescent properties of(R)-5-(9H-carbazol-9-yl)-2-(1,2,3,4-tetrahydronaphthalen-1-yl)isoindoline-1,3-dione((R)-ImNCz),which was recently reported[Chemical Engineering Journal 418129167(2021)].The polarizable continuum model(PCM)and the combined quantum mechanics and molecular mechanics(QM/MM)method are adopted in simulation of the property of the molecule in the gas phase,solvated in acetonitrile and in aggregation states.It is found that large spin–orbit coupling(SOC)constants and a smaller energy gap between the first singlet excited state and the first triplet excited state(△E_(st))in prism-like single crystals(SC_(p)-form)are responsible for the TADF of(R)-lmNCz,while no TADF is found in block-like single crystals(SC_(b)-form)with a larger △E_(st).The multiple ultralong phosphorescence(UOP)peaks in the spectrum are of complex origins,and they are related not only to ImNCz but also to a minor amount of impurities(ImNBd)in the crystal prepared in the laboratory.The dimer has similar phosphorescence emission wavelengths to the(R)-lmNCz-SC_(p) monomers.The complex composed of(R)-lmNCz and(R)-lmNBd contributes to the phosphorescent emission peak at about 600 nm,and the phosphorescent emission peak at about 650 nm is generated by(R)-lmNBd.This indicates that the impurity could also contribute to emission in molecular crystals.The present calculations clarify the relationship between the molecular aggregation and the light-emitting properties of the TADF emitters and will therefore be helpful for the design of potentially more useful TADF emitters.展开更多
Two n-butoxy-encapsulated dendritic thermally activated delayed fluorescent(TADF) emitters(namely O-D1 and O-D2) with the first-/second-generation carbazoledendrons are designed and synthesized via C—N coupling betwe...Two n-butoxy-encapsulated dendritic thermally activated delayed fluorescent(TADF) emitters(namely O-D1 and O-D2) with the first-/second-generation carbazoledendrons are designed and synthesized via C—N coupling between carbazoledendrons and 2,4,6-tris(4-bromophenyl)-1,3,5-triazine core.It is found that,compa red with the commo nly-used tert-butyl groups,the use of n-butoxy encapsulation groups can lead to smallersinglet-triplet energy gap for the dendrimers,producing stronger TADF effect together with faster reverse intersystem crossing process.Solution-processed TADF organic light-emitting diodes(OLEDs) utilizingalkoxy-encapsulated dendrimers O-D1 and O-D2 as emitters exhibitstate-of-the-art device efficiency withthe maximum external quantum efficiency up to 16.8% and 20.6%,respectively,which are ~1.6 and~2.0 times that of the tert-butyl-encapsulated counterparts.These results suggest that alkoxy encapsulation of the carbazole-based TADF dendrimers can be a promising approach for developing highly efficient emitters for solution-processed OLEDs.展开更多
Three carbazole derivatives, Ac PTC, Px PTC and Pt PTC, consisting of two 9,9-dimethyl-9,10-dihydroacridine,phenoxazine or phenothiazine donor groups and one diphenyltriazine acceptor group fixed at 1,8,9-positions of...Three carbazole derivatives, Ac PTC, Px PTC and Pt PTC, consisting of two 9,9-dimethyl-9,10-dihydroacridine,phenoxazine or phenothiazine donor groups and one diphenyltriazine acceptor group fixed at 1,8,9-positions of a single carbazole ring via phenylene, are designed and synthesized. X-ray diffraction analysis of Ac PTC reveals that there exist multiple π-π interactions between the donor and acceptor groups to form a sandwich-like structural unit with edge-to-face interaction model. The compounds thus show obvious thermally activated delayed fluorescence with through-space charge transfer character and possess considerable photoluminescence quantum yields of up to 73% in doped films with sky-blue to yellow emissions. The solution-processed electroluminescent devices achieve the highest maximum external quantum efficiencies of 10.0%, 11% and 5.6% for Ac PTC, Px PTC and Pt PTC, respectively, with small efficiency roll-offs.展开更多
Thermally activated delayed fluorescence(TADF)molecules have attracted great attention as high efficient luminescent materials.Most of TADF molecules possess small energy gap between the first singlet excited state(S_...Thermally activated delayed fluorescence(TADF)molecules have attracted great attention as high efficient luminescent materials.Most of TADF molecules possess small energy gap between the first singlet excited state(S_(1))and the first triplet excited state(T_(1))to favor the up-conversion from T_(1)to S_(1).In this paper,a new TADF generation mechanism is revealed based on theoretical simulation.By systematic study of the light-emitting properties of SOBF-OMe in both toluene and in aggregation state,we find that the single SOBF-OMe could not realize TADF emission due to large energy gap as well as small up-conversion rates between S_(1)and T_(1).Through analysis of dimers,we find that dimers with intermolecular hydrogen bond(H-bond)are responsible for the generation of TADF,since smaller energy gap between S_(1)and T_(1)is found and the emission wavelength is in good agreement with experimental counterpart.The emission properties of SOBF-H are also studied for comparison,which reflect the important role of H-bond.Our theoretical results agree ith experimental results well and confirm the mechanism of H-bond induced TADF.展开更多
The development of highly efficient thermally activated delayed fluorescence(TADF)emitters is persistently pursued for the application of organic light-emitting diodes(OLED)in full-colour display and solid-state light...The development of highly efficient thermally activated delayed fluorescence(TADF)emitters is persistently pursued for the application of organic light-emitting diodes(OLED)in full-colour display and solid-state lighting.Herein,we present a heptagonal intramolecular-lock strategy to design high-performance TADF emitters.As a proof-of-concept,a new type of tribenzotropone(TBP)acceptor has been designed and synthesized by a cascade decarboxylative cyclization of aryl oxoacetic acid derivative with biphenyl boronic acid.Compared with the unlocked benzophenone(BP)acceptor,the TBP acceptor has a highly twisted heptagonal geometry with moderate rigidity and flexibility,which enables a high-performance TADF emitter with a small single-triplet energy gap(ΔE_(ST))of 0.04 e V,a high photoluminescence quantum yield(Φ_(PL))of 99% and a large horizontal orientation factor(Θ_(//))of 84.0%.Consequently,highly efficient OLEDs with an external quantum efficiency as high as 33.8% are assembled,which is significantly higher than those of DPAC-BP with a highly rotatable BP acceptor(23.8%)as well as DPACFO with a rigid fluorenone(FO)acceptor(6.9%).展开更多
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
Carbazole-triazine dendrimers with a bulky terminal substituent were synthesized,and the thermally activated delayed fluorescence(TADF)property was investigated.Compared to unsubstituted carbazole dendrimers,dendrimer...Carbazole-triazine dendrimers with a bulky terminal substituent were synthesized,and the thermally activated delayed fluorescence(TADF)property was investigated.Compared to unsubstituted carbazole dendrimers,dendrimers with bulky terminal substituents showed comparable to better photoluminescence quantum yields(PLQY)in neat films.Phenylfluorene(PF)-substituted dendrimers showed the highest PLQY of 81%,a smallΔEst of 0.06 eV,and the fastest reverse intersystem crossing(RISC)rate of∼1×10^(5 )s^(−1) compared to other dendrimers.Phosphorescence measurements of dendrimers and dendrons(fragments)indicate that the close proximity of the triplet energy of phenylfluorene-substituted carbazole dendrons(^(3)LE)to that of phenylfluorene-substituted dendrimers(^(1)CT,^(3)CT)contributes to RISC promotion and improves TADF efficiency.Terminal modification fine-tunes the energy level and suppresses intermolecular interactions,and this study provides a guideline for designing efficient solution-processable and non-doped TADF materials.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
Comprehensive Summary Conjugated fused-ring structures have attracted extensive attention due to their high molecular rigidity to restrain excited-state relaxation and non-radiative decay,and further to enhance the lu...Comprehensive Summary Conjugated fused-ring structures have attracted extensive attention due to their high molecular rigidity to restrain excited-state relaxation and non-radiative decay,and further to enhance the luminance efficiency for emissive materials.Herein,we develop a series of donor-acceptor type thermally activated delayed fluorescence(TADF)emitters by introducing fused-ring 5H-benzofuro[3,2-c]carbazole(32BFCz)as electron donating unit.Through optimizing the numbers and structure of donor and acceptor moieties,three compounds named 32BFCzA,mCF3BFCzOXD and dCF3BFCzOXD are designed,which are composed by mono-32BFCz/trifluoromethylpicolinonitrile,penta-BFCz/3-(trifluoromethyl)phenyl)-1,3,4-oxadiazol-2-yl)benzene and penta-32BFCz/3,5-bis(trifluoromethyl)phenyl)-1,3,4-oxadiazol-2-yl)benzene as donor/acceptor groups,respectively.展开更多
Through-space charge transfer(TSCT)is regarded as an effective way to develop thermally activated delayed fluorescence(TADF)emitters.Based on this strategy,many molecular frameworks have been proposed,among which spir...Through-space charge transfer(TSCT)is regarded as an effective way to develop thermally activated delayed fluorescence(TADF)emitters.Based on this strategy,many molecular frameworks have been proposed,among which spirobased scaffolds have been extensively studied due to their unique advantages.In this work,we developed three emitters SPS,SPO,and SPON,which were constructed with the same donor and various acceptors to explore the influence of acceptor modulation at the C9 position of fluorene for spirostructure TSCT emitters.The results show that the acceptor with too weak electronwithdrawing ability will cause the emitter to not have TADF properties,while the acceptor with too much steric hindrance will weaken the face-to-faceπ-πstacking interaction between donor/acceptor(D/A).Since SPO balances the electron-withdrawing strength and steric hindrance of the acceptor,it achieves the highest external quantum efficiency(EQE)of 17.75%.This work shows that appropriate acceptor selection is essential for the TADF properties and high efficiency of the spirobased scaffold TSCT emitter.展开更多
Two simple donor-acceptor multifunctional pure organic light-emitting molecules[(9H-carbazol-9-yl)(4-hydroxyphenyl)-methanone(CzMP)and(4-hydroxyphenyl)(10H-phenothiazin-10-yl)methanone(PTZMP)]with distinct aggregation...Two simple donor-acceptor multifunctional pure organic light-emitting molecules[(9H-carbazol-9-yl)(4-hydroxyphenyl)-methanone(CzMP)and(4-hydroxyphenyl)(10H-phenothiazin-10-yl)methanone(PTZMP)]with distinct aggregation-induced emission(AIE)properties were synthesized.Surprisingly,CzMP showed a long room temperature phosphorescence lifetime(>900 ms),and PTZMP exhibited triple emission of prompt fluorescence(PF),room temperature phosphorescence(RTP)and thermally activated delayed fluorescence(TADF).Furthermore,CzMP effectively responded to mechanical external forces and solvent fumigation,exhibiting dual-mode mechanochromic luminescence(MCL)including multiple fluorescence color shifts and phosphorescence switching.Time-dependent density functional theory(TDDFT)calculations were investigated to explain different luminescence properties of the two molecules,and the single crystal of CzMP was obtained and analyzed to demonstrate the unique molecular stacking pattern and strong intermolecular interactions in close association with phosphorescence emission.The multifunctional luminescent properties of the emitters explored in this work could be more effectively applied to a wide range of applications,such as information encryption and anti-counterfeiting.展开更多
Ionic thermally activated delayed fluorescence(TADF)emitters are rarely investigated due to their poor photoluminescence and electroluminescence performance.Herein,highly efficient ionic TADF emitters with charged do...Ionic thermally activated delayed fluorescence(TADF)emitters are rarely investigated due to their poor photoluminescence and electroluminescence performance.Herein,highly efficient ionic TADF emitters with charged donor–acceptor(D–A^(+))and D–A^(+)–D architectures are designed,innovatively based on the phosphonium cation electron acceptor.The symmetric D–A^(+)–D compound in doped film exhibits a high photoluminescence quantum yield of 0.91 and a short emission lifetime of 1.43 microseconds.Partially solution-processed organic lightemitting diodes based on these ionic TADF emitters achieve a maximum external quantum efficiency(EQE)of 18.3%and a peak luminance of 14,532 candelas per square meter(cd/m^(2))and show a small efficiency roll-off of 7.1%(EQE=17%)at a practical high luminance of 1000 cd/m^(2).These results demonstrate the high potential of phosphonium cations as promising electron acceptors to construct TADF emitters for high-performance electroluminescence devices.The current study opens up an appealing way for future exploitation of high-efficiency ionic TADF materials.展开更多
Since polymer-based light-emitting diodes(PLEDs)arewellsuited building blocks for large-area and low-cost flexible display equipment,state-of-the-art thermally activated delayed fluorescence(TADF)PLEDs are in high dem...Since polymer-based light-emitting diodes(PLEDs)arewellsuited building blocks for large-area and low-cost flexible display equipment,state-of-the-art thermally activated delayed fluorescence(TADF)PLEDs are in high demand.To respond to this demand,light-emitting TADF units have initially been modified with electron-transporting units to balance the carrier transport of regiorandom TADF polymers,and simultaneously,an intramolecular sensitizing strategy has also been employed by covalently incorporating TADF sensitizers with light-emitting TADF units and hosts in conjugated polymers to accelerate the spin-flip of triplet excitons.Superior photophysical properties have been achieved by a rational regulation of the proportions of each component,achieving a photoluminescence quantumyield of 90%,an extremely high rate of reverse intersystem crossing of 3×106 s−1,and a relatively low nonradiative decay rate of around 105 s−1.As a result,the solutionprocessed PLEDs can attain an external quantum efficiency(EQE)value of 25.4%with emission peaks of around 550 nm,representing record-high performance for PLEDs.The efficiency roll-off can also be significantly suppressed,maintaining an EQE value of 24.2%at 1000 cd/m2 with ideal efficiency roll-off of lower than 5%.Encouragingly,this work provides a valid strategy to tackle the imperative need for PLEDs with high EQE and low efficiency roll-off.展开更多
High-performance nondoped organic light-emitting diodes(OLEDs)are promising technologies for future commercial applications.Herein,we synthesized two new thermally activated delayed fluorescence(TADF)emitters that ena...High-performance nondoped organic light-emitting diodes(OLEDs)are promising technologies for future commercial applications.Herein,we synthesized two new thermally activated delayed fluorescence(TADF)emitters that enable us,for the first time,to combine three effective approaches for enhancing the efficiency of nondoped OLEDs.First,the two emitters are designed to have high steric hindrances such that their emitting cores will be suitably isolated from those of their neighbors to minimize concentration quenching.On the other hand,each of the two emitters has two stable conformations in solid films.In their neat films,molecules with the minority conformation behave effectively as dopants in the matrix composing of the majority conformation.One hundred percent exciton harvesting is thus theoretically feasible in this unique architecture of“self-doped”neat films.Furthermore,both emitters have relatively high aspect ratios in terms of their molecular shapes.This leads to films with preferred molecular orientations enabling high populations of horizontal dipoles beneficial for optical outcoupling.With these three factors,OLEDs with nondoped emitting layers of the respective emitters both achieve nearly 100%exciton utilization and deliver over 30%external quantum efficiencies and ultralow efficiency roll-off at high brightness,which have not been observed in reported nondoped OLEDs.展开更多
The electrochemiluminescence(ECL)behavior of a multiresonance thermally activated delayed fluorescence molecule has been investigated for the first time by means of ECL‐voltage curves,newly designed ECL‐time observa...The electrochemiluminescence(ECL)behavior of a multiresonance thermally activated delayed fluorescence molecule has been investigated for the first time by means of ECL‐voltage curves,newly designed ECL‐time observatory,and ECL spectroscopy.The compound,Mes3DiKTa,shows complex ECL behavior,including a delayed onset time of 5 ms for ECL generation in both the annihilation pathway and the coreactant route,which we attribute to organic long‐persistent ECL(OLECL).Triplet‐triplet annihilation,thermally activated delayed fluorescence and uncompensated solution resistance cannot be ruled out as contributing mechanisms to the ECL.A very long ECL emission decay was attributed to OLECL as well.The absolute ECL efficiencies of Mes3DiKTa were enhanced and reached 0.0013%in annihilation route and 1.1%for the coreactant system,which are superior to those of most other organic ECL materials.It is plausible that ECL materials with comparable behavior as Mes3DiKTa are desirable in applications such as ECL sensing,imaging,and light‐emitting devices.展开更多
To enhance the potential application of thermally activated delayed fluorescence(TADF)molecular materials,new functions are gradually cooperated to the TADF molecules.Aggregation induced emission can effectively solve...To enhance the potential application of thermally activated delayed fluorescence(TADF)molecular materials,new functions are gradually cooperated to the TADF molecules.Aggregation induced emission can effectively solve the fluorescence quenching problem for TADF molecules in solid phase,thus aggregation-induced delayed fluorescence(AIDF)molecules were recently focused.Nevertheless,their luminescent mechanisms are not clear enough.In this work,excited state properties of an AIDF molecule DMF-BP-DMAC[reported in Chemistry-An Asian Journal 14828(2019)]are theoretically studied in tetrahydrofuran(THF)and solid phase.For consideration of surrounding environment,the polarizable continuum method(PCM)and the combined quantum mechanics and molecular mechanics(QM/MM)method were applied for solvent and solid phase,respectively.Due to the increase of the transition dipole moment and decrease of the energy difference between the first single excited state(S1)and the ground state(S0),the radiative rate is increased by about 2 orders of magnitude in solid phase.The energy dissipation of the non-radiative process from S1 to S0 is mainly contributed by low-frequency vibrational modes in solvent,and they can be effectively suppressed in aggregation,which may lead to a slow non-radiation process in solid phase.Both factors would induce enhanced luminescence efficiency of DMF-BP-DMAC in solid phase.Meanwhile,the small energy gap between S1 and triplet excited states results in high reverse intersystem crossing(RISC)rates in both solvent and solid phase.Therefore,TADF is confirmed in both phases.Aggregation significantly influences both the ISC and RISC processes and more RISC channels are involved in solid state.The enhanced delayed fluorescence should be induced by both the enhanced fluorescent efficiency and ISC efficiency.Our calculation provides a reasonable explanation for experimental measurements and helps one to better understand the luminescence mechanism of AIDF molecules.展开更多
To attain high efficiencies in hybrid white organic light-emitting diodes(WOLEDs),mutual quenching of the fluorophors and phosphors should be minimized.Efforts have been devoted to reducing the triplet quenching of ph...To attain high efficiencies in hybrid white organic light-emitting diodes(WOLEDs),mutual quenching of the fluorophors and phosphors should be minimized.Efforts have been devoted to reducing the triplet quenching of phosphors;however,the quenching of fluorophors by the external heavy-atom effect(EHA)introduced by the phosphors is often ignored.Here,we observed that conventional fluorophors and fluorophors with thermally activated delayed fluorescence(TADF)behave differently in the presence of EHA perturbers.The efficiencies of the conventional fluorophors suffer greatly from the EHA,whereas the TADF fluorophors exhibit negligible changes,which makes TADF materials ideal fluorophors for hybrid devices.WOLEDs using a blue TADF fluorophor and an orange phosphor achieve a maximum forward viewing external quantum efficiency of 19.6%and a maximum forward viewing power efficiency of 50.2 lm W^(-1),among the best values for hybrid WOLEDs.This report is the first time that the EHA effect has been considered in hybrid WOLEDs and that a general strategy toward highly efficient hybrid WOLEDs with simple structures is proposed.展开更多
A purely organic D-π-A-π-D type emitter showing thermally activated delayed fluorescence(TADF)and room temperature phosphorescence(RTP)was designed and synthesized by utilizing the benzophenone as an acceptor and th...A purely organic D-π-A-π-D type emitter showing thermally activated delayed fluorescence(TADF)and room temperature phosphorescence(RTP)was designed and synthesized by utilizing the benzophenone as an acceptor and the N-phenyl-2-napthylamine as a donor moiety.It exhibits considerable TADF character in doped PMMA film and room temperature phosphorescence with a long lifetime of 74 ms at466 nm in solid state.The devices with the configuration of ITO/Mo_(2) O_(3)(4 nm)/mCP(30 nm)/mCP:x wt%NP2 BP/TmTyPB(60 nm)/LiF(1.5 nm)/AI(100 nm)were prepared by vacuum evaporation to explore their electroluminescent performance.Intere stingly,the non-doped device has obtained near-white emission with a fluorescence emission peak at 475 nm and a phosphore scence emission peak at 563 nm having the CIE coordinate of(0.23,0.32)and the maximum external quantum efficiency of 1.09%.展开更多
A series of novel hyperbranched polymers(HBPs) consisting of a 2,7-subsituted 9-(heptadecan-9-yl)-9H-carbazole unit(A_2+A_2') and a tetra-substituted green thermally activated delayed fluorescence(TADF) dye of 2,3...A series of novel hyperbranched polymers(HBPs) consisting of a 2,7-subsituted 9-(heptadecan-9-yl)-9H-carbazole unit(A_2+A_2') and a tetra-substituted green thermally activated delayed fluorescence(TADF) dye of 2,3,5,6-tetra(9Hcarbazol-9-yl)-4-pyridinecarbonitrile(4CzCNPy, B4) have been synthesized via Suzuki cross-coupling reaction following an "A2+A2'+B_4" method. The polymers are named according to the polymerization ratio of 4CzCNPy monomer(5 mol%, 10 mol% and 15 mol% for HBPs of P2-P4 respectively, and 0 mol% for the control linear polymer P1). Their thermal, optoelectronic and electrochemical properties have been characterized by a combination of techniques. All the polymers exhibit high thermal stability with the decomposition temperatures(Td) above 400 ℃ and glass transition temperatures(Tg) up to 98 ℃. Unfortunately, the incorporation of TADF moiety into these HBP materials induced non-TADF characteristics. However, when the HBPs functionalized as the host for our previously developed 4CzCNPy TADF dopant in solution processed devices, maximum external quantum efficiency of 5.7% and current efficiency of 17.9 cd/A have been achieved in P3-based device, which is significantly higher than those of 1.5% and 4.2 cd/A for the linear polymer P1.展开更多
Organic thermally activated delayed fluorescence(TADF)emitters have attracted increasing concerns,owing to their atypical photophysical features that can pave the way to the innovative engineering applications.As cutt...Organic thermally activated delayed fluorescence(TADF)emitters have attracted increasing concerns,owing to their atypical photophysical features that can pave the way to the innovative engineering applications.As cutting-edge type of luminescent molecules,however,most of them only exert a single-wavelength emission from the lowest excited state,according to Kasha’s rule.To develop their potential applications in multicolor luminescence and multi-functional luminescent probes for biological imaging,researchers have begun to turn their attention to design organic TADF molecules with dual-emission characteristics,by employing an additional fluorescence,phosphorescence,or TADF signal within a single-component system.We herein summarized the design principles as well as the luminescence mechanism of organic donor-acceptor TADF compounds with dual-emission characteristics,the superiority of which can cover unique material applications in modern luminescencerelated fields.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11974216,11874242,21933002 and 11904210)Shandong Provincial Natural Science Foundation,China(Grant No.ZR2019MA056)+1 种基金the support of the Taishan Scholar Project of Shandong Provincethe project funded by China Postdoctoral Science Foundation(Grant No.2018M642689)。
文摘Aggregation-induced thermally activated delayed fluorescence(TADF)phenomena have attracted extensive attention recently.In this paper,several theoretical models including monomer,dimer,and complex are used for the explanation of the luminescent properties of(R)-5-(9H-carbazol-9-yl)-2-(1,2,3,4-tetrahydronaphthalen-1-yl)isoindoline-1,3-dione((R)-ImNCz),which was recently reported[Chemical Engineering Journal 418129167(2021)].The polarizable continuum model(PCM)and the combined quantum mechanics and molecular mechanics(QM/MM)method are adopted in simulation of the property of the molecule in the gas phase,solvated in acetonitrile and in aggregation states.It is found that large spin–orbit coupling(SOC)constants and a smaller energy gap between the first singlet excited state and the first triplet excited state(△E_(st))in prism-like single crystals(SC_(p)-form)are responsible for the TADF of(R)-lmNCz,while no TADF is found in block-like single crystals(SC_(b)-form)with a larger △E_(st).The multiple ultralong phosphorescence(UOP)peaks in the spectrum are of complex origins,and they are related not only to ImNCz but also to a minor amount of impurities(ImNBd)in the crystal prepared in the laboratory.The dimer has similar phosphorescence emission wavelengths to the(R)-lmNCz-SC_(p) monomers.The complex composed of(R)-lmNCz and(R)-lmNBd contributes to the phosphorescent emission peak at about 600 nm,and the phosphorescent emission peak at about 650 nm is generated by(R)-lmNBd.This indicates that the impurity could also contribute to emission in molecular crystals.The present calculations clarify the relationship between the molecular aggregation and the light-emitting properties of the TADF emitters and will therefore be helpful for the design of potentially more useful TADF emitters.
基金the financial support from the Science and Technology Development Plan Project of Jilin Province (No.20180520003JH)the Natural Science Fund Project of Changchun University of Science and Technology (No.XQNJJ2017-14)the Youth Innovation Promotion Association of Chinese Academy of Sciences (No.2015180)。
文摘Two n-butoxy-encapsulated dendritic thermally activated delayed fluorescent(TADF) emitters(namely O-D1 and O-D2) with the first-/second-generation carbazoledendrons are designed and synthesized via C—N coupling between carbazoledendrons and 2,4,6-tris(4-bromophenyl)-1,3,5-triazine core.It is found that,compa red with the commo nly-used tert-butyl groups,the use of n-butoxy encapsulation groups can lead to smallersinglet-triplet energy gap for the dendrimers,producing stronger TADF effect together with faster reverse intersystem crossing process.Solution-processed TADF organic light-emitting diodes(OLEDs) utilizingalkoxy-encapsulated dendrimers O-D1 and O-D2 as emitters exhibitstate-of-the-art device efficiency withthe maximum external quantum efficiency up to 16.8% and 20.6%,respectively,which are ~1.6 and~2.0 times that of the tert-butyl-encapsulated counterparts.These results suggest that alkoxy encapsulation of the carbazole-based TADF dendrimers can be a promising approach for developing highly efficient emitters for solution-processed OLEDs.
基金supported by the National Natural Science Foundation of China (Nos. 51973210, 21805271 and 21674110)the Science and Technology Development Project of Jilin Province, China (No. 20190201071JC)。
文摘Three carbazole derivatives, Ac PTC, Px PTC and Pt PTC, consisting of two 9,9-dimethyl-9,10-dihydroacridine,phenoxazine or phenothiazine donor groups and one diphenyltriazine acceptor group fixed at 1,8,9-positions of a single carbazole ring via phenylene, are designed and synthesized. X-ray diffraction analysis of Ac PTC reveals that there exist multiple π-π interactions between the donor and acceptor groups to form a sandwich-like structural unit with edge-to-face interaction model. The compounds thus show obvious thermally activated delayed fluorescence with through-space charge transfer character and possess considerable photoluminescence quantum yields of up to 73% in doped films with sky-blue to yellow emissions. The solution-processed electroluminescent devices achieve the highest maximum external quantum efficiencies of 10.0%, 11% and 5.6% for Ac PTC, Px PTC and Pt PTC, respectively, with small efficiency roll-offs.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11974216,11874242,21933002,and 11904210)the Natural Science Foundation of Shandong Province,China(Grant No.ZR2019MA056)+1 种基金the Taishan Scholar Project of Shandong Province,Chinathe Project funded by China Postdoctoral Science Foundation(Grant No.2018M642689)。
文摘Thermally activated delayed fluorescence(TADF)molecules have attracted great attention as high efficient luminescent materials.Most of TADF molecules possess small energy gap between the first singlet excited state(S_(1))and the first triplet excited state(T_(1))to favor the up-conversion from T_(1)to S_(1).In this paper,a new TADF generation mechanism is revealed based on theoretical simulation.By systematic study of the light-emitting properties of SOBF-OMe in both toluene and in aggregation state,we find that the single SOBF-OMe could not realize TADF emission due to large energy gap as well as small up-conversion rates between S_(1)and T_(1).Through analysis of dimers,we find that dimers with intermolecular hydrogen bond(H-bond)are responsible for the generation of TADF,since smaller energy gap between S_(1)and T_(1)is found and the emission wavelength is in good agreement with experimental counterpart.The emission properties of SOBF-H are also studied for comparison,which reflect the important role of H-bond.Our theoretical results agree ith experimental results well and confirm the mechanism of H-bond induced TADF.
基金supported by the National Natural Science Foundation of China(22275127,22031007,22005204)。
文摘The development of highly efficient thermally activated delayed fluorescence(TADF)emitters is persistently pursued for the application of organic light-emitting diodes(OLED)in full-colour display and solid-state lighting.Herein,we present a heptagonal intramolecular-lock strategy to design high-performance TADF emitters.As a proof-of-concept,a new type of tribenzotropone(TBP)acceptor has been designed and synthesized by a cascade decarboxylative cyclization of aryl oxoacetic acid derivative with biphenyl boronic acid.Compared with the unlocked benzophenone(BP)acceptor,the TBP acceptor has a highly twisted heptagonal geometry with moderate rigidity and flexibility,which enables a high-performance TADF emitter with a small single-triplet energy gap(ΔE_(ST))of 0.04 e V,a high photoluminescence quantum yield(Φ_(PL))of 99% and a large horizontal orientation factor(Θ_(//))of 84.0%.Consequently,highly efficient OLEDs with an external quantum efficiency as high as 33.8% are assembled,which is significantly higher than those of DPAC-BP with a highly rotatable BP acceptor(23.8%)as well as DPACFO with a rigid fluorenone(FO)acceptor(6.9%).
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Ministry of Education,Culture,Sports,Science and Technology,Grant/Award Number:ARIM/JPMXP1222JI0040Japan Society for the Promotion of Science,Grant/Award Numbers:KAKENHI/JP20KK0316,KAKENHI/JP21H05405,KAKENHI/JP22H02055,KAKENHI/JP23H02026,KAKENHI/JP23H03966,KAKENHI/JP20H02801。
文摘Carbazole-triazine dendrimers with a bulky terminal substituent were synthesized,and the thermally activated delayed fluorescence(TADF)property was investigated.Compared to unsubstituted carbazole dendrimers,dendrimers with bulky terminal substituents showed comparable to better photoluminescence quantum yields(PLQY)in neat films.Phenylfluorene(PF)-substituted dendrimers showed the highest PLQY of 81%,a smallΔEst of 0.06 eV,and the fastest reverse intersystem crossing(RISC)rate of∼1×10^(5 )s^(−1) compared to other dendrimers.Phosphorescence measurements of dendrimers and dendrons(fragments)indicate that the close proximity of the triplet energy of phenylfluorene-substituted carbazole dendrons(^(3)LE)to that of phenylfluorene-substituted dendrimers(^(1)CT,^(3)CT)contributes to RISC promotion and improves TADF efficiency.Terminal modification fine-tunes the energy level and suppresses intermolecular interactions,and this study provides a guideline for designing efficient solution-processable and non-doped TADF materials.
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.
基金the National Natural Science Foundation of China(Nos.91833304 and 61761136013).
文摘Comprehensive Summary Conjugated fused-ring structures have attracted extensive attention due to their high molecular rigidity to restrain excited-state relaxation and non-radiative decay,and further to enhance the luminance efficiency for emissive materials.Herein,we develop a series of donor-acceptor type thermally activated delayed fluorescence(TADF)emitters by introducing fused-ring 5H-benzofuro[3,2-c]carbazole(32BFCz)as electron donating unit.Through optimizing the numbers and structure of donor and acceptor moieties,three compounds named 32BFCzA,mCF3BFCzOXD and dCF3BFCzOXD are designed,which are composed by mono-32BFCz/trifluoromethylpicolinonitrile,penta-BFCz/3-(trifluoromethyl)phenyl)-1,3,4-oxadiazol-2-yl)benzene and penta-32BFCz/3,5-bis(trifluoromethyl)phenyl)-1,3,4-oxadiazol-2-yl)benzene as donor/acceptor groups,respectively.
基金financial support from the National Natural Science Foundation of China(Nos.51773141,51873139,61961160731,62175171 and 22175124)funded by the Suzhou Science and Technology Plan Project(No.SYG202010)+2 种基金supported by Suzhou Key Laboratory of Functional Nano&Soft Materials,Collaborative Innovation Center of Suzhou Nano Science&Technologythe 111 ProjectJoint International Research Laboratory of Carbon-Based Functional Materials and Devices。
文摘Through-space charge transfer(TSCT)is regarded as an effective way to develop thermally activated delayed fluorescence(TADF)emitters.Based on this strategy,many molecular frameworks have been proposed,among which spirobased scaffolds have been extensively studied due to their unique advantages.In this work,we developed three emitters SPS,SPO,and SPON,which were constructed with the same donor and various acceptors to explore the influence of acceptor modulation at the C9 position of fluorene for spirostructure TSCT emitters.The results show that the acceptor with too weak electronwithdrawing ability will cause the emitter to not have TADF properties,while the acceptor with too much steric hindrance will weaken the face-to-faceπ-πstacking interaction between donor/acceptor(D/A).Since SPO balances the electron-withdrawing strength and steric hindrance of the acceptor,it achieves the highest external quantum efficiency(EQE)of 17.75%.This work shows that appropriate acceptor selection is essential for the TADF properties and high efficiency of the spirobased scaffold TSCT emitter.
文摘Two simple donor-acceptor multifunctional pure organic light-emitting molecules[(9H-carbazol-9-yl)(4-hydroxyphenyl)-methanone(CzMP)and(4-hydroxyphenyl)(10H-phenothiazin-10-yl)methanone(PTZMP)]with distinct aggregation-induced emission(AIE)properties were synthesized.Surprisingly,CzMP showed a long room temperature phosphorescence lifetime(>900 ms),and PTZMP exhibited triple emission of prompt fluorescence(PF),room temperature phosphorescence(RTP)and thermally activated delayed fluorescence(TADF).Furthermore,CzMP effectively responded to mechanical external forces and solvent fumigation,exhibiting dual-mode mechanochromic luminescence(MCL)including multiple fluorescence color shifts and phosphorescence switching.Time-dependent density functional theory(TDDFT)calculations were investigated to explain different luminescence properties of the two molecules,and the single crystal of CzMP was obtained and analyzed to demonstrate the unique molecular stacking pattern and strong intermolecular interactions in close association with phosphorescence emission.The multifunctional luminescent properties of the emitters explored in this work could be more effectively applied to a wide range of applications,such as information encryption and anti-counterfeiting.
基金This research was made possible as a result of a generous grant from the Key Research Program of Frontier Science,the Chinese Academy of Sciences(CAS)(grant no.QYZDJ-SSW-SLH033)the National Natural Science Foundation of China(grant no.52073286)+3 种基金the Natural Science Foundation of Fujian Province(grant no.2006L2005)the Fujian Science and Technology Innovation Laboratory for Optoelectronic Information of China(grant nos.2021ZR132 and 2021ZZ115)the Youth Innovation Foundation of Xiamen City(grant nos.3502Z20206082 and 3502Z20206083)the Major Research Project of Xiamen(grant no.3502Z20191015).
文摘Ionic thermally activated delayed fluorescence(TADF)emitters are rarely investigated due to their poor photoluminescence and electroluminescence performance.Herein,highly efficient ionic TADF emitters with charged donor–acceptor(D–A^(+))and D–A^(+)–D architectures are designed,innovatively based on the phosphonium cation electron acceptor.The symmetric D–A^(+)–D compound in doped film exhibits a high photoluminescence quantum yield of 0.91 and a short emission lifetime of 1.43 microseconds.Partially solution-processed organic lightemitting diodes based on these ionic TADF emitters achieve a maximum external quantum efficiency(EQE)of 18.3%and a peak luminance of 14,532 candelas per square meter(cd/m^(2))and show a small efficiency roll-off of 7.1%(EQE=17%)at a practical high luminance of 1000 cd/m^(2).These results demonstrate the high potential of phosphonium cations as promising electron acceptors to construct TADF emitters for high-performance electroluminescence devices.The current study opens up an appealing way for future exploitation of high-efficiency ionic TADF materials.
基金the National Natural Science Foundation of China(nos.51922021 and 52103220)the Shandong Provincial Natural Science Foundation(no.ZR2019ZD50).
文摘Since polymer-based light-emitting diodes(PLEDs)arewellsuited building blocks for large-area and low-cost flexible display equipment,state-of-the-art thermally activated delayed fluorescence(TADF)PLEDs are in high demand.To respond to this demand,light-emitting TADF units have initially been modified with electron-transporting units to balance the carrier transport of regiorandom TADF polymers,and simultaneously,an intramolecular sensitizing strategy has also been employed by covalently incorporating TADF sensitizers with light-emitting TADF units and hosts in conjugated polymers to accelerate the spin-flip of triplet excitons.Superior photophysical properties have been achieved by a rational regulation of the proportions of each component,achieving a photoluminescence quantumyield of 90%,an extremely high rate of reverse intersystem crossing of 3×106 s−1,and a relatively low nonradiative decay rate of around 105 s−1.As a result,the solutionprocessed PLEDs can attain an external quantum efficiency(EQE)value of 25.4%with emission peaks of around 550 nm,representing record-high performance for PLEDs.The efficiency roll-off can also be significantly suppressed,maintaining an EQE value of 24.2%at 1000 cd/m2 with ideal efficiency roll-off of lower than 5%.Encouragingly,this work provides a valid strategy to tackle the imperative need for PLEDs with high EQE and low efficiency roll-off.
基金National Natural Science Foundation of China,Grant/Award Numbers:51821002,52003185,52003186,52130304National Key Research&Development Program of China,Grant/Award Numbers:2020YFA0714601,2020YFA0714604+2 种基金Suzhou Key Laboratory of Functional Nano&Soft MaterialsCollaborative Innovation Center of Suzhou Nano Science&Technologythe 111 Project。
文摘High-performance nondoped organic light-emitting diodes(OLEDs)are promising technologies for future commercial applications.Herein,we synthesized two new thermally activated delayed fluorescence(TADF)emitters that enable us,for the first time,to combine three effective approaches for enhancing the efficiency of nondoped OLEDs.First,the two emitters are designed to have high steric hindrances such that their emitting cores will be suitably isolated from those of their neighbors to minimize concentration quenching.On the other hand,each of the two emitters has two stable conformations in solid films.In their neat films,molecules with the minority conformation behave effectively as dopants in the matrix composing of the majority conformation.One hundred percent exciton harvesting is thus theoretically feasible in this unique architecture of“self-doped”neat films.Furthermore,both emitters have relatively high aspect ratios in terms of their molecular shapes.This leads to films with preferred molecular orientations enabling high populations of horizontal dipoles beneficial for optical outcoupling.With these three factors,OLEDs with nondoped emitting layers of the respective emitters both achieve nearly 100%exciton utilization and deliver over 30%external quantum efficiencies and ultralow efficiency roll-off at high brightness,which have not been observed in reported nondoped OLEDs.
基金supports to this study by Natural Sciences and Engineering Research Council Canada(NSERC,DG RGPIN‐2018‐06556 and SPG STPGP‐2016‐493924)Canada Foundation of Innovation/Ontario Innovation Trust(CFI/OIT,9040)The University of Western Ontario.
文摘The electrochemiluminescence(ECL)behavior of a multiresonance thermally activated delayed fluorescence molecule has been investigated for the first time by means of ECL‐voltage curves,newly designed ECL‐time observatory,and ECL spectroscopy.The compound,Mes3DiKTa,shows complex ECL behavior,including a delayed onset time of 5 ms for ECL generation in both the annihilation pathway and the coreactant route,which we attribute to organic long‐persistent ECL(OLECL).Triplet‐triplet annihilation,thermally activated delayed fluorescence and uncompensated solution resistance cannot be ruled out as contributing mechanisms to the ECL.A very long ECL emission decay was attributed to OLECL as well.The absolute ECL efficiencies of Mes3DiKTa were enhanced and reached 0.0013%in annihilation route and 1.1%for the coreactant system,which are superior to those of most other organic ECL materials.It is plausible that ECL materials with comparable behavior as Mes3DiKTa are desirable in applications such as ECL sensing,imaging,and light‐emitting devices.
基金the National Natural Science Foundation of China(Grant Nos.11874242,11974216,and 11904210)Shandong Provincial Natural Science Foundation,China(Grant No.ZR2019MA056)Taishan Scholar Project of Shandong Province,China,and the China Postdoctoral Science Foundation(Grant No.2018M642689).
文摘To enhance the potential application of thermally activated delayed fluorescence(TADF)molecular materials,new functions are gradually cooperated to the TADF molecules.Aggregation induced emission can effectively solve the fluorescence quenching problem for TADF molecules in solid phase,thus aggregation-induced delayed fluorescence(AIDF)molecules were recently focused.Nevertheless,their luminescent mechanisms are not clear enough.In this work,excited state properties of an AIDF molecule DMF-BP-DMAC[reported in Chemistry-An Asian Journal 14828(2019)]are theoretically studied in tetrahydrofuran(THF)and solid phase.For consideration of surrounding environment,the polarizable continuum method(PCM)and the combined quantum mechanics and molecular mechanics(QM/MM)method were applied for solvent and solid phase,respectively.Due to the increase of the transition dipole moment and decrease of the energy difference between the first single excited state(S1)and the ground state(S0),the radiative rate is increased by about 2 orders of magnitude in solid phase.The energy dissipation of the non-radiative process from S1 to S0 is mainly contributed by low-frequency vibrational modes in solvent,and they can be effectively suppressed in aggregation,which may lead to a slow non-radiation process in solid phase.Both factors would induce enhanced luminescence efficiency of DMF-BP-DMAC in solid phase.Meanwhile,the small energy gap between S1 and triplet excited states results in high reverse intersystem crossing(RISC)rates in both solvent and solid phase.Therefore,TADF is confirmed in both phases.Aggregation significantly influences both the ISC and RISC processes and more RISC channels are involved in solid state.The enhanced delayed fluorescence should be induced by both the enhanced fluorescent efficiency and ISC efficiency.Our calculation provides a reasonable explanation for experimental measurements and helps one to better understand the luminescence mechanism of AIDF molecules.
基金We would like to thank the National Natural Science Foundation of China(Grant Nos.51173096,21161160447 and 61177023)for financial support.
文摘To attain high efficiencies in hybrid white organic light-emitting diodes(WOLEDs),mutual quenching of the fluorophors and phosphors should be minimized.Efforts have been devoted to reducing the triplet quenching of phosphors;however,the quenching of fluorophors by the external heavy-atom effect(EHA)introduced by the phosphors is often ignored.Here,we observed that conventional fluorophors and fluorophors with thermally activated delayed fluorescence(TADF)behave differently in the presence of EHA perturbers.The efficiencies of the conventional fluorophors suffer greatly from the EHA,whereas the TADF fluorophors exhibit negligible changes,which makes TADF materials ideal fluorophors for hybrid devices.WOLEDs using a blue TADF fluorophor and an orange phosphor achieve a maximum forward viewing external quantum efficiency of 19.6%and a maximum forward viewing power efficiency of 50.2 lm W^(-1),among the best values for hybrid WOLEDs.This report is the first time that the EHA effect has been considered in hybrid WOLEDs and that a general strategy toward highly efficient hybrid WOLEDs with simple structures is proposed.
基金absolutely supported by Program for National Natural Scientific Foundation of China(Nos.91833304,61904120,61775155,61705158)Natural Science Foundation of Shanxi Province(Nos.201901D211090,201903D121100,201801D221124)+1 种基金the Fundamental Research Funds for the Central Universities,Shanxi Provincial Key Innovative Research Team in Science and Technology(No.201601D021043)the Joint Research Funds of Department of Science&Technology of Shaanxi Province and Northwestern Polytechnical University(No.2020GXLH-Z-006)。
文摘A purely organic D-π-A-π-D type emitter showing thermally activated delayed fluorescence(TADF)and room temperature phosphorescence(RTP)was designed and synthesized by utilizing the benzophenone as an acceptor and the N-phenyl-2-napthylamine as a donor moiety.It exhibits considerable TADF character in doped PMMA film and room temperature phosphorescence with a long lifetime of 74 ms at466 nm in solid state.The devices with the configuration of ITO/Mo_(2) O_(3)(4 nm)/mCP(30 nm)/mCP:x wt%NP2 BP/TmTyPB(60 nm)/LiF(1.5 nm)/AI(100 nm)were prepared by vacuum evaporation to explore their electroluminescent performance.Intere stingly,the non-doped device has obtained near-white emission with a fluorescence emission peak at 475 nm and a phosphore scence emission peak at 563 nm having the CIE coordinate of(0.23,0.32)and the maximum external quantum efficiency of 1.09%.
基金financially supported by the National Natural Science Foundation of China(No.21304047)Natural Science Foundation of Jiangsu Province(No.BK2016042)Research Fund for the Doctoral Program of Higher Education(No.20133221120015)
文摘A series of novel hyperbranched polymers(HBPs) consisting of a 2,7-subsituted 9-(heptadecan-9-yl)-9H-carbazole unit(A_2+A_2') and a tetra-substituted green thermally activated delayed fluorescence(TADF) dye of 2,3,5,6-tetra(9Hcarbazol-9-yl)-4-pyridinecarbonitrile(4CzCNPy, B4) have been synthesized via Suzuki cross-coupling reaction following an "A2+A2'+B_4" method. The polymers are named according to the polymerization ratio of 4CzCNPy monomer(5 mol%, 10 mol% and 15 mol% for HBPs of P2-P4 respectively, and 0 mol% for the control linear polymer P1). Their thermal, optoelectronic and electrochemical properties have been characterized by a combination of techniques. All the polymers exhibit high thermal stability with the decomposition temperatures(Td) above 400 ℃ and glass transition temperatures(Tg) up to 98 ℃. Unfortunately, the incorporation of TADF moiety into these HBP materials induced non-TADF characteristics. However, when the HBPs functionalized as the host for our previously developed 4CzCNPy TADF dopant in solution processed devices, maximum external quantum efficiency of 5.7% and current efficiency of 17.9 cd/A have been achieved in P3-based device, which is significantly higher than those of 1.5% and 4.2 cd/A for the linear polymer P1.
基金supported by Taiyuan University of Technology and the National Natural Science Foundation of China(21975046)。
文摘Organic thermally activated delayed fluorescence(TADF)emitters have attracted increasing concerns,owing to their atypical photophysical features that can pave the way to the innovative engineering applications.As cutting-edge type of luminescent molecules,however,most of them only exert a single-wavelength emission from the lowest excited state,according to Kasha’s rule.To develop their potential applications in multicolor luminescence and multi-functional luminescent probes for biological imaging,researchers have begun to turn their attention to design organic TADF molecules with dual-emission characteristics,by employing an additional fluorescence,phosphorescence,or TADF signal within a single-component system.We herein summarized the design principles as well as the luminescence mechanism of organic donor-acceptor TADF compounds with dual-emission characteristics,the superiority of which can cover unique material applications in modern luminescencerelated fields.