Multi-resonance thermally ac-tivated delayed fluorescence(MR-TADF)emitters are one of the most excellent materi-als for high performance or-ganic light-emitting diodes(OLEDs)with high color puri-ty benefiting from the...Multi-resonance thermally ac-tivated delayed fluorescence(MR-TADF)emitters are one of the most excellent materi-als for high performance or-ganic light-emitting diodes(OLEDs)with high color puri-ty benefiting from their nar-row full width at half maxi-mum(FWHM)and great de-vice performance.However,small spin-orbit coupling(SOC)is one of drawbacks for MR-TADF emitters and introduction of heavy atoms may be one effective solution.In this work,four MR-TADF molecules with different atoms(O,S,Se)are carried out based on the first-principles calculation,and excited state dynamics in both toluene and solid phase is investi-gated.Our calculation results indicate that heavy atoms could induce smaller adiabatic ener-gy gap and larger SOC between the first singlet excited state and the first triplet excited state,which is advantageous for the conversion of singlet and triplet excitons,and thus the generation of thermally activated delayed fluorescence(TADF).Though the reorganization energy and full width at half maximum(FWHM)of emission are increased,the influence is quite limited.Besides,the fluorescent rates are also little influenced.Our calculation results indicate that heavy atom introduction is an efficient strategy to enhance the SOC values of MR-TADF emitters without influencing other properties significantly.展开更多
Thermally activated delayed fluorescence(TADF)and room temperature phosphorescence(RTP)molecules hold promising application prospects in the field of organic light emitting diodes(OLEDs),primarily attributed to their ...Thermally activated delayed fluorescence(TADF)and room temperature phosphorescence(RTP)molecules hold promising application prospects in the field of organic light emitting diodes(OLEDs),primarily attributed to their significant advantages in enhancing device stability and lumines-cence efficiency.Notably,TADF and RTP molecules can achieve nearly 100%exciton utilization without necessitating costly and limited precious metal elements.However,the primary challenges confronting TADF and RTP molecules at present encompass limitations in emission color,low luminescence efficien-cy,severe efficiency roll-off and so on.Given these points,this paper presents a comprehensive overview of the latest research progress in TADF and RTP molecules.We delve into the mechanisms by which TADF molecules achieve efficient fluorescence emission through unique molecular structural designs,fre-quently involving sophisticated intramolecular charge transfer processes and precise energy level modula-tion.Simultaneously,we provide an in-depth analysis of the unique luminescence properties and photo-physical mechanisms of RTP molecules.Furthermore,the article focuses on the design strategies for TADF and RTP molecules,encompassing the manipulation of molecular structures,electronic structures and the enhancement of charge transfer effects.By examining these strategies,we aim to provide a com-prehensive perspective on the research of TADF and RTP molecules.We hope that through this review,it could offer some guidance for future research and inspire the exploration of more innovative TADF and RTP molecules.展开更多
The development of organic materials with white-light emission and thermally activated delayed fluorescence(TADF)properties in the solid state remain a challenge.Herein,a series of white-light-emitting organic luminog...The development of organic materials with white-light emission and thermally activated delayed fluorescence(TADF)properties in the solid state remain a challenge.Herein,a series of white-light-emitting organic luminogens have been developed and are found to show aggregation-induced delayed fluorescence(AIDF)characteristics.The AIDF emitters present dual-emission consisted of prompt fluorescence and TADF in the crystalline state.Their white-light emissions can be easily tuned by altering the chemical structure and connecting position of the heterocyclic aromatic substituent.Under the stimuli of mechanical force and solvent vapor,the compounds exhibit remarkable and reversible mechanochromism,in which their emission colors are switchable between white and yellow.Upon grinding,they also display linearly tunable luminescence colors,as well as force-induced TADF enhancement,which may be associated with the more compact molecular packing and the restriction of intramolecular motions.The results from time-resolved emission scanning and theoretical calculation suggest that the dual-emission of the AIDF luminogens likely results from the twisted intramolecular charge transfer transitions of the molecules,and the reversible mechanochromism properties probably stem from the interconversion of the quasi-axial and the quasi-equatorial conformations.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
Three kinds of triazine based organic molecules designed for thermally activated delayed fluorescence （TADF） emitters are investigated by first-principles calculations. An optimal Hartree-Fork （HF） method is adopt...Three kinds of triazine based organic molecules designed for thermally activated delayed fluorescence （TADF） emitters are investigated by first-principles calculations. An optimal Hartree-Fork （HF） method is adopted for the calculation of energy gap between the first singlet state （S1） and the first triplet state （T1）. The natural transition orbital, the electron- hole （e-h） distribution and the e-h overlap diagram indicate that the S1 states for the three systems include both charge-transfer and some localized excitation component. Further quantitative analysis of the excitation property is performed by introducing the index Ar and the integral of e-h overlap S. It is found that symmetric geometry is a necessary condition for TADF emitters, which can provide more delocalized transition orbitals and consequently a small S1-T1 energy gap. Artful inserting aromatic groups between donors and acceptors can significantly enhance the oscillator strength. Finally, the energy state structures calculated with the optimal HF method is presented, which can provide basis for the study of the dynamics of excited states.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
The development of fluorescent materials capable of harvesting triplet excitons efficiently is of great importance in achieving high-performance low-cost organic light-emitting diodes（OLEDs）.Among the three mechanis...The development of fluorescent materials capable of harvesting triplet excitons efficiently is of great importance in achieving high-performance low-cost organic light-emitting diodes（OLEDs）.Among the three mechanisms converting triplet to singlet excitons,triplet fusion delayed fluorescence（TFDF） plays a key role in the demonstration of highly efficient and reliable OLEDs,especially blue devices,for practice applications.This review focuses on the recent development of TFDF materials and their applications in OLEDs.Fundamental TFDF mechanism,molecular design principles,and the structure-property relationship of TFDF materials with a particular emphasis on their different excited state characters,are presented and discussed.Moreover,the future perspectives and ongoing challenges of TFDF materials are also highlighted.展开更多
Numerous researchers have paid attention to achieve metal-free phosphorescence by exploring new structures or new mechanisms.Herein,a facile way is introduced to endow a common fluorescence dye,tetrabromofluorescein(4...Numerous researchers have paid attention to achieve metal-free phosphorescence by exploring new structures or new mechanisms.Herein,a facile way is introduced to endow a common fluorescence dye,tetrabromofluorescein(4 Br-Flu),some fabulous optical characteristics such as dual emission including thermally activated delayed fluorescence,room-temperature phosphorescence(RTP),and the excellent pH-sensitivity.Shortly,4 Br-Flu with good light-emitting properties is composed into the polymer system.The multiple bromine atoms promote the spin-orbit coupling effect and facilitate triplet excitation.Especially,the hydrogen bonding network of the polymer restricts the molecular motion of4 Br-Flu so that the system can emit long-wavelength RTP when 4 Br-Flu is doped into polyvinyl alcohol or co-polymerized with acrylamide.Due to the reversible transformation of protonation and deprotonation,the 4 Br-Flu based polymer responded to acid and alkali like a phosphorescent switch which makes it an excellent hydrogen chloride/ammonia gas leak detector in dry environment.展开更多
Thermally activated delayed fluorescent(TADF) materials capable of efficient solution-processed nondoped organic light-emitting diodes(OLEDs) are of important and practical significance for further development of OLED...Thermally activated delayed fluorescent(TADF) materials capable of efficient solution-processed nondoped organic light-emitting diodes(OLEDs) are of important and practical significance for further development of OLEDs. In this work, a new electron-donating segment, 2,7-di(9 H-carbazol-9-yl)-9,9-dimethyl-9,10-dihydroacridine(2 Cz-DMAC), was designed to develop solution-processable non-doped TADF emitters. 2 Cz-DMAC can not only simultaneously increase the solubility of compounds and suppress harmful aggregation-caused quenching, but also efficiently broaden the delocalization of the highest occupied molecular orbital and promote the reverse intersystem crossing process. Three new TADF emitters, 2-(2,7-di(9 H-carbazol-9-yl)-9,9-dimethylacridin-10(9 H)-yl)dibenzo[b,d]thiophene 5,5-dioxide(2 Cz-DMAC-BTB), 2-(2,7-di(9 H-carbazol-9-yl)-9,9-dimethylacridin-10(9 H)-yl)-9 H-thioxanthen-9-one(2 Cz-DMAC-TXO), 2-(2,7-di(9 H-carbazol-9-yl)-9,9-dimethylacridin-10(9 H)-yl)thianthrene 5,5,10,10-tetraoxide(2 Cz-DMAC-TTR), were developed by using 2 Cz-DMAC segment as the electron-donor. As anticipated, the solution-processed non-doped OLEDs employing 2 Cz-DMAC-BTB, 2 Cz-DMAC-TXO and 2 CzDMAC-TTR as the emitters respectively exhibited green, orange and red emissions with maximum external quantum efficiencies of 14.0%, 6.6% and 2.9%. These results successfully demonstrate the feasibility and convenience of developing efficient solution-processable non-doped TADF emitters based on 2 CzDMAC segment.展开更多
2,7-Di（9,9-dimethyl-9H-fluoren-l-yl）-9H-thioxanthen-9-one （DMBFTX） with thermally activated delayed fluorescence （TADF） was well designed and synthesized. The phosphorescent organic lightemitting device （PHOLED...2,7-Di（9,9-dimethyl-9H-fluoren-l-yl）-9H-thioxanthen-9-one （DMBFTX） with thermally activated delayed fluorescence （TADF） was well designed and synthesized. The phosphorescent organic lightemitting device （PHOLED） based on this novel TADF host material displays a stable red phosphorescence region, a peak external quantum efficiency （EQE） value of 12.9% and a low EQE roll-off of 38.8%at a luminance of 10000 cd/m2, which is benefited from the reverse intersystem crossing （RISC） of TADF host and less populated triplet exitons. Notably, the red device based on the TADF host DMBFrX exhibits superior electroluminescence performance and reduced efficiency roll-offcompared with the one hosted by commercially available host 1,3-bis（9-carbazolyl）benzene （mCP）, illustrating the high potential of employing the TADF host material with small energy gap to reduce efficiency roll-off in PHOLED.展开更多
High efficiency, stable organic light-emitting diodes （OLEDs） based on 2-pheyl-4＇-carbazole-9-H-Thioxanthen-9- one-10, 10-dioxide （TXO-PhCz） with different doping concentration are constructed. The stability of t...High efficiency, stable organic light-emitting diodes （OLEDs） based on 2-pheyl-4＇-carbazole-9-H-Thioxanthen-9- one-10, 10-dioxide （TXO-PhCz） with different doping concentration are constructed. The stability of the encap- sulated devices are investigated in detail. The devices with the 10 wt% doped TXO-PhCz emitter layer （EML） show the best performance with a current efficiency of 52.1 cd/A, a power efficiency of 32.71re^W, and an external quantum efficiency （EQE） of 17.7%. The devices based on the lOwt%-doped TXO-PhCz EML show the best operational stability with a half-life time （LTSO） of 8Oh, which is 8 h longer than that of the reference devices based on fac-tris（2-phenylpyridinato）iridium（ Ⅲ） （Ir（ppy）a）. These indicate excellent stability of TXO-PhCz for redox and oxidation processes under electrical excitation and TXO-PhCz can be potentially used as the emitters for OLEDs with high efficiency and excellent stability. The high-performance device based on TXO-PhCz with high stability can be further improved by the optimization of the encapsulation technology and the development of a new host for TXO-PhCz.展开更多
A new kind of emissive small-molecular organic cage has been developed via the combination of coupling and condensation reactions,which shows outstanding solubility,structural stability and potential spatial isomeric ...A new kind of emissive small-molecular organic cage has been developed via the combination of coupling and condensation reactions,which shows outstanding solubility,structural stability and potential spatial isomeric chirality.Interestingly,through the introduction of proper donor and acceptor units,this emissive organic cage is the first among organic cages to exhibit red aggregation-induced delayed fluorescence with photoluminescence emission at 603 nm.The finding not only expands the types of emissive small-molecular organic cages,but also represents an important step for further development of red delayed fluorescence materials with good solubility and aggregation-induced emission feature.展开更多
Thermally activated delayed fluorescence（TADF） emitters are primarily comprised of intramolecular charge-transfer（ICT） molecules with small energy difference between the lowest singlet and triplet excited states.T...Thermally activated delayed fluorescence（TADF） emitters are primarily comprised of intramolecular charge-transfer（ICT） molecules with small energy difference between the lowest singlet and triplet excited states.They lend extremely favorable electroluminescent performance to organic light-emitting diodes（OLEDs）.This paper summarizes relevant issues and research efforts in the theoretical prediction of singlet- and triplet-transition energies of ICT molecules via time-dependent density functional theory（TDDFT）.The successful application of the descriptor-based optimal Hartree-Fock percentage method and the optimally tuned range-separated functional to many TADF systems represent an interesting approach to the exact prediction of the complex excited-state molecular dynamics within TDDFT.展开更多
The highest efficiency thermally activated delayed fluorescence(TADF)emitters in OLEDs are mostly based on twisted donor/acceptor(D/A)type organic molecules.Herein,we report the rational molecular design on twisted al...The highest efficiency thermally activated delayed fluorescence(TADF)emitters in OLEDs are mostly based on twisted donor/acceptor(D/A)type organic molecules.Herein,we report the rational molecular design on twisted all ortho-linked carbazole/oxadiazole(Cz/OXD)hybrids with tunable D-A interactions by adjusting the numbers of donor/acceptor units and electron-donating abilities.Singlet-triplet energy bandgaps(ΔEST)are facilely tuned from^0.4,0.15 to^0 eV in D-A,D-A-D to A-D-A type compounds.This variation correlates well with triplet-excited-state frontier orbital spatial separation efficiency.NonTADF feature with solid state photoluminescence quantum yield(PLQY)<10%is observed in D-A type 2CzOXD and D-A-D type 4CzOXD.Owing to the extremely lowΔEST for efficient reverse intersystem crossing,strong TADF with PLQY of 71%-92%is achieved in A-D-A type 4CzDOXD and 4tCzDOXD.High external quantum efficiency from 19.4%to 22.6%is achieved in A-D-A typed 4CzDOXD and 4tCzDOXD.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
By applying two donor-acceptor motif molecules,5,10-di(pyridin-4-yl)-5,10-dihydrophenazine(L1)and 10,10'-di(pyridin-3-yl)-10H,10'H-9,9'-spiroacridine(L2),as ligands and CuI/AgCF3CO2 as metal salt,we synthe...By applying two donor-acceptor motif molecules,5,10-di(pyridin-4-yl)-5,10-dihydrophenazine(L1)and 10,10'-di(pyridin-3-yl)-10H,10'H-9,9'-spiroacridine(L2),as ligands and CuI/AgCF3CO2 as metal salt,we synthesized three coordination polymers,namely,{Cu4(L1)2I4}(CP1),{Cu(L2)I·CHCl3}(CP2)and{Ag(L2)CO2CF3·CHCl3}(CP3).X-ray crystallographic analysis revealed that three coordination polymers all feature one-dimensional(1D)linear chains which are consisting of molecular boxlike units.In comparison with low photoluminescence quantum yield(PLQY)of two ligands,three coordination polymers,CP1,CP2 and CP3,present more intense photoluminescence with PLQY of 15%,46%and 34%at room temperature respectively.The PL emission of CP1 and CP2 at room temperature could be attributed to the fast phosphorescence with lifetime both around 5 ms due to effective intersystem crossing(ISC).Whilst,it is worth noting that CP3 exhibit thermally activated delayed fluorescence(TADF)emission at room temperature.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
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
Three new emitters,namely 10,10’-(quinoline-2,8-diyl)bis(10 H-phenoxazine)(Fene),10,10’-(quinoline-2,8-diyl)bis(10 H-phenothiazine)(Fens) and 10,10’-(quinoline-2,8-diyl)bis(9,9-dimethyl-9,10-dihydroacridine)(Yad),f...Three new emitters,namely 10,10’-(quinoline-2,8-diyl)bis(10 H-phenoxazine)(Fene),10,10’-(quinoline-2,8-diyl)bis(10 H-phenothiazine)(Fens) and 10,10’-(quinoline-2,8-diyl)bis(9,9-dimethyl-9,10-dihydroacridine)(Yad),featuring quinoline as a new electron acceptor have been designed and conveniently synthesized.These emitters possessed small singlet-triplet splitting energy(ΔEst) and twisted structures,which not only endowed them show thermally activated delayed fluorescence(TADF)properties but also afforded a remarkable aggregation-induced emission(AIE) feature.Moreover,they also showed aggregation-induced delayed fluorescence(AIDF) property and good photoluminescence(PL) property,which are the ideal emitters for non-doped organic light-emitting diodes(OLEDs).Furthermore,high-performance non-doped OLEDs based on Fene,Fens and Yad were achieved,and excelle nt maximum external quantum efficiencies(EQEmax) of 14,9%,13.1% and 17,4%,respectively,were obtained.It was also found that all devices exhibited relatively low turn-on voltages ranging from 3.0 V to3.2 V probably due to their twisted conformation and the AIDF properties.These results demonstrated the quinoline-based emitters could have a promising application in non-doped OLEDs.展开更多
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
基金supported by the National Natural Science Foundation of China(No.11974216,No.12374269)the support of the Taishan Scholar Project of Shandong Province。
文摘Multi-resonance thermally ac-tivated delayed fluorescence(MR-TADF)emitters are one of the most excellent materi-als for high performance or-ganic light-emitting diodes(OLEDs)with high color puri-ty benefiting from their nar-row full width at half maxi-mum(FWHM)and great de-vice performance.However,small spin-orbit coupling(SOC)is one of drawbacks for MR-TADF emitters and introduction of heavy atoms may be one effective solution.In this work,four MR-TADF molecules with different atoms(O,S,Se)are carried out based on the first-principles calculation,and excited state dynamics in both toluene and solid phase is investi-gated.Our calculation results indicate that heavy atoms could induce smaller adiabatic ener-gy gap and larger SOC between the first singlet excited state and the first triplet excited state,which is advantageous for the conversion of singlet and triplet excitons,and thus the generation of thermally activated delayed fluorescence(TADF).Though the reorganization energy and full width at half maximum(FWHM)of emission are increased,the influence is quite limited.Besides,the fluorescent rates are also little influenced.Our calculation results indicate that heavy atom introduction is an efficient strategy to enhance the SOC values of MR-TADF emitters without influencing other properties significantly.
基金supported by the National Natural Science Foundation of China(12274266,12374269,12104248 and 12474258)supporting of the Open Fund of the State Key Laboratory of Luminescent Materials and Devices(South China University of Technology)and Taishan Scholar Project of Shandong Province.
文摘Thermally activated delayed fluorescence(TADF)and room temperature phosphorescence(RTP)molecules hold promising application prospects in the field of organic light emitting diodes(OLEDs),primarily attributed to their significant advantages in enhancing device stability and lumines-cence efficiency.Notably,TADF and RTP molecules can achieve nearly 100%exciton utilization without necessitating costly and limited precious metal elements.However,the primary challenges confronting TADF and RTP molecules at present encompass limitations in emission color,low luminescence efficien-cy,severe efficiency roll-off and so on.Given these points,this paper presents a comprehensive overview of the latest research progress in TADF and RTP molecules.We delve into the mechanisms by which TADF molecules achieve efficient fluorescence emission through unique molecular structural designs,fre-quently involving sophisticated intramolecular charge transfer processes and precise energy level modula-tion.Simultaneously,we provide an in-depth analysis of the unique luminescence properties and photo-physical mechanisms of RTP molecules.Furthermore,the article focuses on the design strategies for TADF and RTP molecules,encompassing the manipulation of molecular structures,electronic structures and the enhancement of charge transfer effects.By examining these strategies,we aim to provide a com-prehensive perspective on the research of TADF and RTP molecules.We hope that through this review,it could offer some guidance for future research and inspire the exploration of more innovative TADF and RTP molecules.
基金supported by the National Natural Science Foundation of China(No.51603233)the Natural Science Foundation of Guangdong Province of China(Nos.2019A1515010550,2020A1515010439,2019A1515011389)the GDUPS(2019)the Opening Foundation of Key Laboratory for Polymeric Composite and Functional Materials of Ministry of Education(Sun Yat-sen University,No.PCFM-2019-05)。
文摘The development of organic materials with white-light emission and thermally activated delayed fluorescence(TADF)properties in the solid state remain a challenge.Herein,a series of white-light-emitting organic luminogens have been developed and are found to show aggregation-induced delayed fluorescence(AIDF)characteristics.The AIDF emitters present dual-emission consisted of prompt fluorescence and TADF in the crystalline state.Their white-light emissions can be easily tuned by altering the chemical structure and connecting position of the heterocyclic aromatic substituent.Under the stimuli of mechanical force and solvent vapor,the compounds exhibit remarkable and reversible mechanochromism,in which their emission colors are switchable between white and yellow.Upon grinding,they also display linearly tunable luminescence colors,as well as force-induced TADF enhancement,which may be associated with the more compact molecular packing and the restriction of intramolecular motions.The results from time-resolved emission scanning and theoretical calculation suggest that the dual-emission of the AIDF luminogens likely results from the twisted intramolecular charge transfer transitions of the molecules,and the reversible mechanochromism properties probably stem from the interconversion of the quasi-axial and the quasi-equatorial conformations.
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.
文摘Three kinds of triazine based organic molecules designed for thermally activated delayed fluorescence （TADF） emitters are investigated by first-principles calculations. An optimal Hartree-Fork （HF） method is adopted for the calculation of energy gap between the first singlet state （S1） and the first triplet state （T1）. The natural transition orbital, the electron- hole （e-h） distribution and the e-h overlap diagram indicate that the S1 states for the three systems include both charge-transfer and some localized excitation component. Further quantitative analysis of the excitation property is performed by introducing the index Ar and the integral of e-h overlap S. It is found that symmetric geometry is a necessary condition for TADF emitters, which can provide more delocalized transition orbitals and consequently a small S1-T1 energy gap. Artful inserting aromatic groups between donors and acceptors can significantly enhance the oscillator strength. Finally, the energy state structures calculated with the optimal HF method is presented, which can provide basis for the study of the dynamics of excited states.
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supported by National Natural Science Foundation of China(No.21372168)
文摘The development of fluorescent materials capable of harvesting triplet excitons efficiently is of great importance in achieving high-performance low-cost organic light-emitting diodes（OLEDs）.Among the three mechanisms converting triplet to singlet excitons,triplet fusion delayed fluorescence（TFDF） plays a key role in the demonstration of highly efficient and reliable OLEDs,especially blue devices,for practice applications.This review focuses on the recent development of TFDF materials and their applications in OLEDs.Fundamental TFDF mechanism,molecular design principles,and the structure-property relationship of TFDF materials with a particular emphasis on their different excited state characters,are presented and discussed.Moreover,the future perspectives and ongoing challenges of TFDF materials are also highlighted.
基金financially supported by the National Natural Science Foundation of China(Nos.21788102,22020102006,21722603 and 21871083)Shanghai Municipal Science and Technology Major Project(No.2018SHZDZX03)+3 种基金Program of Shanghai Academic/Technology Research Leader(No.20XD1421300)‘Shu Guang’project supported by Shanghai Municipal Education Commission and Shanghai Education Development Foundation(No.19SG26)the Innovation Program of Shanghai Municipal Education Commission(No.2017-01-07-00-02-E00010)the Fundamental Research Funds for the Central Universities。
文摘Numerous researchers have paid attention to achieve metal-free phosphorescence by exploring new structures or new mechanisms.Herein,a facile way is introduced to endow a common fluorescence dye,tetrabromofluorescein(4 Br-Flu),some fabulous optical characteristics such as dual emission including thermally activated delayed fluorescence,room-temperature phosphorescence(RTP),and the excellent pH-sensitivity.Shortly,4 Br-Flu with good light-emitting properties is composed into the polymer system.The multiple bromine atoms promote the spin-orbit coupling effect and facilitate triplet excitation.Especially,the hydrogen bonding network of the polymer restricts the molecular motion of4 Br-Flu so that the system can emit long-wavelength RTP when 4 Br-Flu is doped into polyvinyl alcohol or co-polymerized with acrylamide.Due to the reversible transformation of protonation and deprotonation,the 4 Br-Flu based polymer responded to acid and alkali like a phosphorescent switch which makes it an excellent hydrogen chloride/ammonia gas leak detector in dry environment.
基金supported by the National Natural Science Foundation of China (Nos.51773029,52073040 and 51821002)the Fundamental Research Funds for the Central Universities (No.ZYGX2016Z010)the International Cooperation and Exchange Project of Science and Technology Department of Sichuan Province (No.2019YFH0057)。
文摘Thermally activated delayed fluorescent(TADF) materials capable of efficient solution-processed nondoped organic light-emitting diodes(OLEDs) are of important and practical significance for further development of OLEDs. In this work, a new electron-donating segment, 2,7-di(9 H-carbazol-9-yl)-9,9-dimethyl-9,10-dihydroacridine(2 Cz-DMAC), was designed to develop solution-processable non-doped TADF emitters. 2 Cz-DMAC can not only simultaneously increase the solubility of compounds and suppress harmful aggregation-caused quenching, but also efficiently broaden the delocalization of the highest occupied molecular orbital and promote the reverse intersystem crossing process. Three new TADF emitters, 2-(2,7-di(9 H-carbazol-9-yl)-9,9-dimethylacridin-10(9 H)-yl)dibenzo[b,d]thiophene 5,5-dioxide(2 Cz-DMAC-BTB), 2-(2,7-di(9 H-carbazol-9-yl)-9,9-dimethylacridin-10(9 H)-yl)-9 H-thioxanthen-9-one(2 Cz-DMAC-TXO), 2-(2,7-di(9 H-carbazol-9-yl)-9,9-dimethylacridin-10(9 H)-yl)thianthrene 5,5,10,10-tetraoxide(2 Cz-DMAC-TTR), were developed by using 2 Cz-DMAC segment as the electron-donor. As anticipated, the solution-processed non-doped OLEDs employing 2 Cz-DMAC-BTB, 2 Cz-DMAC-TXO and 2 CzDMAC-TTR as the emitters respectively exhibited green, orange and red emissions with maximum external quantum efficiencies of 14.0%, 6.6% and 2.9%. These results successfully demonstrate the feasibility and convenience of developing efficient solution-processable non-doped TADF emitters based on 2 CzDMAC segment.
基金supported by National Natural Science Foundation of China(No. 61605158)the Science and TechnologyDepartment of Shaanxi Province(No. 2016JQ2028)the Education Department of Shaanxi Province(No. 16JK1790)
文摘2,7-Di（9,9-dimethyl-9H-fluoren-l-yl）-9H-thioxanthen-9-one （DMBFTX） with thermally activated delayed fluorescence （TADF） was well designed and synthesized. The phosphorescent organic lightemitting device （PHOLED） based on this novel TADF host material displays a stable red phosphorescence region, a peak external quantum efficiency （EQE） value of 12.9% and a low EQE roll-off of 38.8%at a luminance of 10000 cd/m2, which is benefited from the reverse intersystem crossing （RISC） of TADF host and less populated triplet exitons. Notably, the red device based on the TADF host DMBFrX exhibits superior electroluminescence performance and reduced efficiency roll-offcompared with the one hosted by commercially available host 1,3-bis（9-carbazolyl）benzene （mCP）, illustrating the high potential of employing the TADF host material with small energy gap to reduce efficiency roll-off in PHOLED.
基金Supported by the National Natural Science Foundation of China under Grant Nos 61420106002,51373189,61178061,and 61227008the Hundred Talents Program of the Chinese Academy of Sciences,the National Basic Research Program of China under Grant No 2014CB932600the Start-Up Fund of the Technical Institute of Physics and Chemistry of the Chinese Academy of Sciences
文摘High efficiency, stable organic light-emitting diodes （OLEDs） based on 2-pheyl-4＇-carbazole-9-H-Thioxanthen-9- one-10, 10-dioxide （TXO-PhCz） with different doping concentration are constructed. The stability of the encap- sulated devices are investigated in detail. The devices with the 10 wt% doped TXO-PhCz emitter layer （EML） show the best performance with a current efficiency of 52.1 cd/A, a power efficiency of 32.71re^W, and an external quantum efficiency （EQE） of 17.7%. The devices based on the lOwt%-doped TXO-PhCz EML show the best operational stability with a half-life time （LTSO） of 8Oh, which is 8 h longer than that of the reference devices based on fac-tris（2-phenylpyridinato）iridium（ Ⅲ） （Ir（ppy）a）. These indicate excellent stability of TXO-PhCz for redox and oxidation processes under electrical excitation and TXO-PhCz can be potentially used as the emitters for OLEDs with high efficiency and excellent stability. The high-performance device based on TXO-PhCz with high stability can be further improved by the optimization of the encapsulation technology and the development of a new host for TXO-PhCz.
基金financially supported by the National Natural Science Foundation of China(Nos.51521002 and 21905048)the Foundation of Guangzhou Science and Technology Project(No.201707020019)+1 种基金the Program for Science and Technology Development of Dongguan(No.2019622163009)the startup grants from Dongguan University of Technology for high-level talent(No.KCYKYQD2017018)。
文摘A new kind of emissive small-molecular organic cage has been developed via the combination of coupling and condensation reactions,which shows outstanding solubility,structural stability and potential spatial isomeric chirality.Interestingly,through the introduction of proper donor and acceptor units,this emissive organic cage is the first among organic cages to exhibit red aggregation-induced delayed fluorescence with photoluminescence emission at 603 nm.The finding not only expands the types of emissive small-molecular organic cages,but also represents an important step for further development of red delayed fluorescence materials with good solubility and aggregation-induced emission feature.
基金the Exploratory Research for Advanced Technology (ERATO) of Japanthe Key Special Program of the Ministry of Science and Technology of China(No.2016YFB0401000) for financial support
文摘Thermally activated delayed fluorescence（TADF） emitters are primarily comprised of intramolecular charge-transfer（ICT） molecules with small energy difference between the lowest singlet and triplet excited states.They lend extremely favorable electroluminescent performance to organic light-emitting diodes（OLEDs）.This paper summarizes relevant issues and research efforts in the theoretical prediction of singlet- and triplet-transition energies of ICT molecules via time-dependent density functional theory（TDDFT）.The successful application of the descriptor-based optimal Hartree-Fock percentage method and the optimally tuned range-separated functional to many TADF systems represent an interesting approach to the exact prediction of the complex excited-state molecular dynamics within TDDFT.
基金National Natural Science Foundation of China(Nos.91833304,61805211)National Key Research and Development Program of China for the Joint Research Program between China and European Union(No.2016YFE0112000)+1 种基金the Natural Science Foundation of Jiangsu Province(Nos.BK20160042 and XYDXX-026)the Foundation for the Author of National Excellent Doctoral Dissertation of China FANEDD(No.201436)
文摘The highest efficiency thermally activated delayed fluorescence(TADF)emitters in OLEDs are mostly based on twisted donor/acceptor(D/A)type organic molecules.Herein,we report the rational molecular design on twisted all ortho-linked carbazole/oxadiazole(Cz/OXD)hybrids with tunable D-A interactions by adjusting the numbers of donor/acceptor units and electron-donating abilities.Singlet-triplet energy bandgaps(ΔEST)are facilely tuned from^0.4,0.15 to^0 eV in D-A,D-A-D to A-D-A type compounds.This variation correlates well with triplet-excited-state frontier orbital spatial separation efficiency.NonTADF feature with solid state photoluminescence quantum yield(PLQY)<10%is observed in D-A type 2CzOXD and D-A-D type 4CzOXD.Owing to the extremely lowΔEST for efficient reverse intersystem crossing,strong TADF with PLQY of 71%-92%is achieved in A-D-A type 4CzDOXD and 4tCzDOXD.High external quantum efficiency from 19.4%to 22.6%is achieved in A-D-A typed 4CzDOXD and 4tCzDOXD.
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financially supported by the National Natural Science Foundation (Nos.21772116,21671122 and 21475078)the Shandong Taishan Scholar’s Construction Project,JSPS KAKENHI (No.JP17H01232)the Japan Science and Technology Agency (JST),ERATO,Adachi Molecular Exciton Engineering Project,under JST ERATO (No.JPMJER1305),Japan
文摘By applying two donor-acceptor motif molecules,5,10-di(pyridin-4-yl)-5,10-dihydrophenazine(L1)and 10,10'-di(pyridin-3-yl)-10H,10'H-9,9'-spiroacridine(L2),as ligands and CuI/AgCF3CO2 as metal salt,we synthesized three coordination polymers,namely,{Cu4(L1)2I4}(CP1),{Cu(L2)I·CHCl3}(CP2)and{Ag(L2)CO2CF3·CHCl3}(CP3).X-ray crystallographic analysis revealed that three coordination polymers all feature one-dimensional(1D)linear chains which are consisting of molecular boxlike units.In comparison with low photoluminescence quantum yield(PLQY)of two ligands,three coordination polymers,CP1,CP2 and CP3,present more intense photoluminescence with PLQY of 15%,46%and 34%at room temperature respectively.The PL emission of CP1 and CP2 at room temperature could be attributed to the fast phosphorescence with lifetime both around 5 ms due to effective intersystem crossing(ISC).Whilst,it is worth noting that CP3 exhibit thermally activated delayed fluorescence(TADF)emission at room temperature.
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.
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the National Natural Science Foundation of China (Nos.91956119,21871272,21521002) for financial supports。
文摘Three new emitters,namely 10,10’-(quinoline-2,8-diyl)bis(10 H-phenoxazine)(Fene),10,10’-(quinoline-2,8-diyl)bis(10 H-phenothiazine)(Fens) and 10,10’-(quinoline-2,8-diyl)bis(9,9-dimethyl-9,10-dihydroacridine)(Yad),featuring quinoline as a new electron acceptor have been designed and conveniently synthesized.These emitters possessed small singlet-triplet splitting energy(ΔEst) and twisted structures,which not only endowed them show thermally activated delayed fluorescence(TADF)properties but also afforded a remarkable aggregation-induced emission(AIE) feature.Moreover,they also showed aggregation-induced delayed fluorescence(AIDF) property and good photoluminescence(PL) property,which are the ideal emitters for non-doped organic light-emitting diodes(OLEDs).Furthermore,high-performance non-doped OLEDs based on Fene,Fens and Yad were achieved,and excelle nt maximum external quantum efficiencies(EQEmax) of 14,9%,13.1% and 17,4%,respectively,were obtained.It was also found that all devices exhibited relatively low turn-on voltages ranging from 3.0 V to3.2 V probably due to their twisted conformation and the AIDF properties.These results demonstrated the quinoline-based emitters could have a promising application in non-doped OLEDs.
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.
