Thermally activated delayed fluorescence(TADF)molecules have outstanding potential for applications in organic light-emitting diodes(OLEDs).Due to the lack of systematic studies on the correlation between molecular st...Thermally activated delayed fluorescence(TADF)molecules have outstanding potential for applications in organic light-emitting diodes(OLEDs).Due to the lack of systematic studies on the correlation between molecular structure and luminescence properties,TADF molecules are far from meeting the needs of practical applications in terms of variety and number.In this paper,three twisted TADF molecules are studied and their photophysical properties are theoretically predicted based on the thermal vibrational correlation function method combined with multiscale calculations.The results show that all the molecules exhibit fast reverse intersystem crossing(RISC)rates(kRISC),predicting their TADF luminescence properties.In addition,the binding of DHPAzSi as the donor unit with different acceptors can change the dihedral angle between the ground and excited states,and the planarity of the acceptors is positively correlated with the reorganization energy,a property that has a strong influence on the non-radiative process.Furthermore,a decrease in the energy of the molecular charge transfer state and an increase in the kRISC were observed in the films.This study not only provides a reliable explanation for the observed experimental results,but also offers valuable insights that can guide the design of future TADF molecules.展开更多
A four-coordinate mononuclear cuprous complex oCBP-Cu-Pym(1, oCBP =1,2-bis(diphenylphosphine)-nido-carborane, Pym = 2-methyl-6-(1 H-pyrazol-1-yl)pyridine) was synthe-sized and characterized by elemental analysis, NMR,...A four-coordinate mononuclear cuprous complex oCBP-Cu-Pym(1, oCBP =1,2-bis(diphenylphosphine)-nido-carborane, Pym = 2-methyl-6-(1 H-pyrazol-1-yl)pyridine) was synthe-sized and characterized by elemental analysis, NMR, UV-Vis and X-ray single-crystal structure analysis. It crystallizes in monoclinic space group C2/c with a = 28.4182(8), b =16.2994(4), c = 22.2708(5) ?, β = 127.219(2)°, V = 8214.8(3) ?3, Z = 8, Mr = 766.92, ρcalc = 1.24 g/cm3, F(000) = 3160, μ = 2.30 mm–1, GOOF = 1.063, the final R = 0.0700 and wR = 0.1903 for7158 observed reflections with I > 2σ(I). The Cu(I) ion adopts a highly distorted tetrahedral geometry defined by two nitrogen and two phosphorous atoms. Under UV 365 nm at room temperature, this complex exhibits green emission with maximum emission peak at 516 nm,lifetime 32.4 μs and quantum yield(ф = 0.461) in the solid state. Photophysical investigation suggests that the emission of complex 1 at room temperature was attributed to TADF, which is strongly supported by theoretic calculation.展开更多
A four-coordinate mononuclear cuprous complex [Cu（ac1m）POP]BF4·0.5（C6H14）· 0.5（C2H5OH）（1, ac1 m = 2-（2-ethoxyphenyl）-1-phenyl-1H-imidazo[4,5-f][1,10]phenanthroline, POP = bis[2-（dipenylphosphino）p...A four-coordinate mononuclear cuprous complex [Cu（ac1m）POP]BF4·0.5（C6H14）· 0.5（C2H5OH）（1, ac1 m = 2-（2-ethoxyphenyl）-1-phenyl-1H-imidazo[4,5-f][1,10]phenanthroline, POP = bis[2-（dipenylphosphino）phenyl]ether） was synthesized and characterized by elemental analysis, NMR, UV-vis, cyclic voltammetry and X-ray single-crystal structure analysis. It crystallizes in monoclinic space group P21/c with a = 17.0546（19）, b = 15.4650（17）, c = 23.685（2） A, β = 104.007（11）°, V = 6061.1（12）A^3, Z = 4, Mr = 1171.46, Dc = 1.284 g/cm^3, F（000） = 2432, μ = 1.50 mm^–1, GOOF = 1.070, the final R = 0.059 and wR = 0.1640 for 8952 observed reflections with I 〉 2σ（Ⅰ）. Compound 1 is composed of a BF4-anion and a [Cu（ac1m）POP]^＋ cation. The Cu（Ⅰ） ion adopts a tetrahedral coordination geometry defined by two nitrogen and two phosphorous atoms. The complex exhibits yellow luminescence with maximum emission peaks at 546 nm, lifetimes 15.1 μs and quantum yields（ф = 0.130） at room temperature. The complex displays thermally activated delayed fluorescence（TADF） at room temperature, which is proved experimentally and theoretically. And the organic light-emitting diode（OLED） with 1 as the light emitting material has the maximum current efficiency of 5.86 cd/A and the highest brightness of 3215 cd/m^2.展开更多
White organic light-emitting diodes(WOLEDs)show very promising as next-generation light-sources,but achieving high power efficiency(PE)and long operational lifetime remains challenging because of the lack of stable bl...White organic light-emitting diodes(WOLEDs)show very promising as next-generation light-sources,but achieving high power efficiency(PE)and long operational lifetime remains challenging because of the lack of stable blue emitters that can harvest all triplet(T_(1))excitons for light emission.Herein,we propose integrating stable azure multiresonance thermally activated delayed fluorescent(MR-TADF)emitters into tri-color hybrid WOLEDs to tackle these issues.By meticulously selecting MR-TADF emitters and precisely tuning the exciton recombination zone,the optimized tri-color devices based on BCzBN-3B achieve color-stable white light emission with maximum external quantum efficiency(EQE_(max))and maximum PE(PE_(max))of 34.4%and 101.8 Im W^(-1),respectively.Furthermore,the LTgo,defined as the time for the luminance to drop to 90%of its initial value at 1000 cd m^(-2),reaches 761 h.In addition,a hybrid WOLED with deep blue emitter developed using our strategy achieves a high color rendering index of 88 and an EQE_(max) of 30.6%,further demonstrating the versatility and effectiveness of our approach.The record-breaking efficiency and ultra-long lifetime underscore the success of hybrid white-light devices by incorporating robust blue MR-TADF emitters.These advancements open new avenues for commercialization of hybrid WOLEDs,presenting promising solutions for energy-efficient lighting and display technologies.展开更多
Cross-linkable hole transport materials(x-HTMs)play a crucial role in solving the issue of interlayer mixing of solution-processed organic light-emitting diodes(OLEDs).However,issues such as energy level mismatch and ...Cross-linkable hole transport materials(x-HTMs)play a crucial role in solving the issue of interlayer mixing of solution-processed organic light-emitting diodes(OLEDs).However,issues such as energy level mismatch and low hole mobility hinder the application of x-HTMs in deep-blue OLEDs.In particular,thermally activated delayed fluorescent(TADF)emitters require HTMs with high triplet energies(E T)to ensure high exciton utilization efficiency.Here,two star-shaped cross-linkable HTMs 5-(9H-carbazol-9-yl)-N^(1),N^(3)-di(p-tolyl)-N^(1),N^(3)-bis(4-vinylphenyl)benzene-1,3-diamine(m-V-CzDPA)and N^(1),N^(1)-diphenyl-N^(3),N^(5)-di(p-tolyl)-N^(3),N^(5)-bis(4-vinylphenyl)benzene-1,3,5-triamine(m-V-DPADPA)were designed and synthesized.Owing to their aromatic torsion structures,m-V-CzDPA and m-V-DPADPA possessed high E Ts of 2.89 and 2.87 eV,respectively,which can effectively confine triplet excitons in the emitting layer(EML).The carrier diffusion coefficients of their x-HTMs,x-m-CzDPA and x-m-DPADPA,which were obtained via carrier diffusion imaging characterization were 0.54 and 0.44 cm^(2) s^(-1),respectively,thus indicating outstanding intrinsic hole transport capacity,with hole mobilities of 4.30×10^(-4) and 1.39×10^(-4) cm^(2) V^(-1) s^(-1),respectively.Solution-processed deep-blue TADF-OLEDs employing x-m-CzDPA as the HTM achieved a maximum current efficiency/maximum external quantum efficiency of 5.25 cd A^(-1)/18.06%,with CIE coordinates of(0.162,0.042).This is the first time that x-HTMs have served as efficient deep-blue TADF-OLEDs via a solution process,which also meets the latest BT.2020 standard(CIE_(y)≤0.046).展开更多
Solution-processed fluorescent organic light-emitting diodes(OLEDs)are believed to be favorable for low-cost,large-area,and flexible displays but still suffer from the limited external quantum efficiency(EQE)below 5%....Solution-processed fluorescent organic light-emitting diodes(OLEDs)are believed to be favorable for low-cost,large-area,and flexible displays but still suffer from the limited external quantum efficiency(EQE)below 5%.Herein,we demonstrate the EQE breakthrough by introducing a donor–acceptor type thermally activated delayed fluorescence(TADF)polymer as the sensitizer for the typical green-emitting fluorescent dopants.Benefitting from their matched energy alignment,the unwanted trap-assisted recombination directly on fluorescent dopant is prevented to avoid the additional loss of triplet excitons.Indeed,triplet excitons are mainly formed on the polymeric TADF sensitizer via a Langevin recombination and then spin-flipped to singlet excitons due to the good upconversion capability.Followed by an efficient Förster energy transfer,both singlet and triplet excitons can be harvested by fluorescent dopants,leading to a promising solution-processed green hyperfluorescence with a record-high EQE of 21.2%(72.2cd/A,59.7lm/W)and Commission Internationale de L'Eclairage coordinates of(0.32,0.59).The results clearly highlight the great potential of solution-processed fluorescent OLEDs based on TADF polymers as the sensitizer.展开更多
Understanding the host-vip interactions for thermally activated delayed fluorescence(TADF)emitters is critical because the interactions between the host matrices and TADF emitters enable precise control on the optoe...Understanding the host-vip interactions for thermally activated delayed fluorescence(TADF)emitters is critical because the interactions between the host matrices and TADF emitters enable precise control on the optoelectronic performance,whereas technologically manipulating the singlet and triplet excitons by using different kinds of host-vip interactions remains elusive.Here,we report a comprehensive picture that rationalizes host-vip interaction-modulated exciton recombination by using time-resolved spectroscopy.We found that the early-time relaxation is accelerated in polar polymer because dipole-dipole interaction facilitates the stabilization of the 1CT state.However,an opposite trend is observed in longer delay time,and faster decay in the less polar polymer is ascribed to theπ-πinteraction that plays the dominant role in the later stage of the excited state.Our findings highlight the technological engineering singlet and triplet excitons using different kinds of host-vip interactions based on their electronic characteristics.展开更多
文摘Thermally activated delayed fluorescence(TADF)molecules have outstanding potential for applications in organic light-emitting diodes(OLEDs).Due to the lack of systematic studies on the correlation between molecular structure and luminescence properties,TADF molecules are far from meeting the needs of practical applications in terms of variety and number.In this paper,three twisted TADF molecules are studied and their photophysical properties are theoretically predicted based on the thermal vibrational correlation function method combined with multiscale calculations.The results show that all the molecules exhibit fast reverse intersystem crossing(RISC)rates(kRISC),predicting their TADF luminescence properties.In addition,the binding of DHPAzSi as the donor unit with different acceptors can change the dihedral angle between the ground and excited states,and the planarity of the acceptors is positively correlated with the reorganization energy,a property that has a strong influence on the non-radiative process.Furthermore,a decrease in the energy of the molecular charge transfer state and an increase in the kRISC were observed in the films.This study not only provides a reliable explanation for the observed experimental results,but also offers valuable insights that can guide the design of future TADF molecules.
基金supported by the National Natural Science Foundation of China(21373221,21521061,51672271,21671190,21403236)the Natural Science Foundation of Fujian Province(2006L2005)
文摘A four-coordinate mononuclear cuprous complex oCBP-Cu-Pym(1, oCBP =1,2-bis(diphenylphosphine)-nido-carborane, Pym = 2-methyl-6-(1 H-pyrazol-1-yl)pyridine) was synthe-sized and characterized by elemental analysis, NMR, UV-Vis and X-ray single-crystal structure analysis. It crystallizes in monoclinic space group C2/c with a = 28.4182(8), b =16.2994(4), c = 22.2708(5) ?, β = 127.219(2)°, V = 8214.8(3) ?3, Z = 8, Mr = 766.92, ρcalc = 1.24 g/cm3, F(000) = 3160, μ = 2.30 mm–1, GOOF = 1.063, the final R = 0.0700 and wR = 0.1903 for7158 observed reflections with I > 2σ(I). The Cu(I) ion adopts a highly distorted tetrahedral geometry defined by two nitrogen and two phosphorous atoms. Under UV 365 nm at room temperature, this complex exhibits green emission with maximum emission peak at 516 nm,lifetime 32.4 μs and quantum yield(ф = 0.461) in the solid state. Photophysical investigation suggests that the emission of complex 1 at room temperature was attributed to TADF, which is strongly supported by theoretic calculation.
基金supported by the National Natural Science Foundation of China(21373221,21521061,51672271,21671190,21403236)the Natural Science Foundation of Fujian Province(2006L2005)
文摘A four-coordinate mononuclear cuprous complex [Cu（ac1m）POP]BF4·0.5（C6H14）· 0.5（C2H5OH）（1, ac1 m = 2-（2-ethoxyphenyl）-1-phenyl-1H-imidazo[4,5-f][1,10]phenanthroline, POP = bis[2-（dipenylphosphino）phenyl]ether） was synthesized and characterized by elemental analysis, NMR, UV-vis, cyclic voltammetry and X-ray single-crystal structure analysis. It crystallizes in monoclinic space group P21/c with a = 17.0546（19）, b = 15.4650（17）, c = 23.685（2） A, β = 104.007（11）°, V = 6061.1（12）A^3, Z = 4, Mr = 1171.46, Dc = 1.284 g/cm^3, F（000） = 2432, μ = 1.50 mm^–1, GOOF = 1.070, the final R = 0.059 and wR = 0.1640 for 8952 observed reflections with I 〉 2σ（Ⅰ）. Compound 1 is composed of a BF4-anion and a [Cu（ac1m）POP]^＋ cation. The Cu（Ⅰ） ion adopts a tetrahedral coordination geometry defined by two nitrogen and two phosphorous atoms. The complex exhibits yellow luminescence with maximum emission peaks at 546 nm, lifetimes 15.1 μs and quantum yields（ф = 0.130） at room temperature. The complex displays thermally activated delayed fluorescence（TADF） at room temperature, which is proved experimentally and theoretically. And the organic light-emitting diode（OLED） with 1 as the light emitting material has the maximum current efficiency of 5.86 cd/A and the highest brightness of 3215 cd/m^2.
基金support from the National Natural ScienceFoundationof China(52373192 and52130308)Research Team Cultivation Program of Shenzhen University(Grant No.2023DFT004)+1 种基金Natural Science Foundation of Guangdong Province(2024A1515030199)the Shenzhen Science and Technology Program(ZDSYS20210623091813040 and 20220810164838001)。
文摘White organic light-emitting diodes(WOLEDs)show very promising as next-generation light-sources,but achieving high power efficiency(PE)and long operational lifetime remains challenging because of the lack of stable blue emitters that can harvest all triplet(T_(1))excitons for light emission.Herein,we propose integrating stable azure multiresonance thermally activated delayed fluorescent(MR-TADF)emitters into tri-color hybrid WOLEDs to tackle these issues.By meticulously selecting MR-TADF emitters and precisely tuning the exciton recombination zone,the optimized tri-color devices based on BCzBN-3B achieve color-stable white light emission with maximum external quantum efficiency(EQE_(max))and maximum PE(PE_(max))of 34.4%and 101.8 Im W^(-1),respectively.Furthermore,the LTgo,defined as the time for the luminance to drop to 90%of its initial value at 1000 cd m^(-2),reaches 761 h.In addition,a hybrid WOLED with deep blue emitter developed using our strategy achieves a high color rendering index of 88 and an EQE_(max) of 30.6%,further demonstrating the versatility and effectiveness of our approach.The record-breaking efficiency and ultra-long lifetime underscore the success of hybrid white-light devices by incorporating robust blue MR-TADF emitters.These advancements open new avenues for commercialization of hybrid WOLEDs,presenting promising solutions for energy-efficient lighting and display technologies.
基金supported by the National Key Research and Development Program of China(2021YFB3602702)the National Natural Science Foundation of China(52173180).
文摘Cross-linkable hole transport materials(x-HTMs)play a crucial role in solving the issue of interlayer mixing of solution-processed organic light-emitting diodes(OLEDs).However,issues such as energy level mismatch and low hole mobility hinder the application of x-HTMs in deep-blue OLEDs.In particular,thermally activated delayed fluorescent(TADF)emitters require HTMs with high triplet energies(E T)to ensure high exciton utilization efficiency.Here,two star-shaped cross-linkable HTMs 5-(9H-carbazol-9-yl)-N^(1),N^(3)-di(p-tolyl)-N^(1),N^(3)-bis(4-vinylphenyl)benzene-1,3-diamine(m-V-CzDPA)and N^(1),N^(1)-diphenyl-N^(3),N^(5)-di(p-tolyl)-N^(3),N^(5)-bis(4-vinylphenyl)benzene-1,3,5-triamine(m-V-DPADPA)were designed and synthesized.Owing to their aromatic torsion structures,m-V-CzDPA and m-V-DPADPA possessed high E Ts of 2.89 and 2.87 eV,respectively,which can effectively confine triplet excitons in the emitting layer(EML).The carrier diffusion coefficients of their x-HTMs,x-m-CzDPA and x-m-DPADPA,which were obtained via carrier diffusion imaging characterization were 0.54 and 0.44 cm^(2) s^(-1),respectively,thus indicating outstanding intrinsic hole transport capacity,with hole mobilities of 4.30×10^(-4) and 1.39×10^(-4) cm^(2) V^(-1) s^(-1),respectively.Solution-processed deep-blue TADF-OLEDs employing x-m-CzDPA as the HTM achieved a maximum current efficiency/maximum external quantum efficiency of 5.25 cd A^(-1)/18.06%,with CIE coordinates of(0.162,0.042).This is the first time that x-HTMs have served as efficient deep-blue TADF-OLEDs via a solution process,which also meets the latest BT.2020 standard(CIE_(y)≤0.046).
基金National Natural Science Foundation of China,Grant/Award Numbers:52273198,52173186,21961160720Yunnan Fundamental Research Projects,Grant/Award Numbers:202301BF070001-008,K264202230134+2 种基金The Yunling Scholar Project of“Yunnan Revitalization Talent Support Program”Natural Science Foundation of Jilin Province,Grant/Award Number:20230101358JCYouth Innovation Promotion Association。
文摘Solution-processed fluorescent organic light-emitting diodes(OLEDs)are believed to be favorable for low-cost,large-area,and flexible displays but still suffer from the limited external quantum efficiency(EQE)below 5%.Herein,we demonstrate the EQE breakthrough by introducing a donor–acceptor type thermally activated delayed fluorescence(TADF)polymer as the sensitizer for the typical green-emitting fluorescent dopants.Benefitting from their matched energy alignment,the unwanted trap-assisted recombination directly on fluorescent dopant is prevented to avoid the additional loss of triplet excitons.Indeed,triplet excitons are mainly formed on the polymeric TADF sensitizer via a Langevin recombination and then spin-flipped to singlet excitons due to the good upconversion capability.Followed by an efficient Förster energy transfer,both singlet and triplet excitons can be harvested by fluorescent dopants,leading to a promising solution-processed green hyperfluorescence with a record-high EQE of 21.2%(72.2cd/A,59.7lm/W)and Commission Internationale de L'Eclairage coordinates of(0.32,0.59).The results clearly highlight the great potential of solution-processed fluorescent OLEDs based on TADF polymers as the sensitizer.
基金Strategic Priority Research Program of the Chinese Academy of Sciences,Grant/Award Number:XDB0450202Chinese Academy of Sciences,Grant/Award Number:YSBR-007National Natural Science Foundation of China,Grant/Award Numbers:22203085,22273095。
文摘Understanding the host-vip interactions for thermally activated delayed fluorescence(TADF)emitters is critical because the interactions between the host matrices and TADF emitters enable precise control on the optoelectronic performance,whereas technologically manipulating the singlet and triplet excitons by using different kinds of host-vip interactions remains elusive.Here,we report a comprehensive picture that rationalizes host-vip interaction-modulated exciton recombination by using time-resolved spectroscopy.We found that the early-time relaxation is accelerated in polar polymer because dipole-dipole interaction facilitates the stabilization of the 1CT state.However,an opposite trend is observed in longer delay time,and faster decay in the less polar polymer is ascribed to theπ-πinteraction that plays the dominant role in the later stage of the excited state.Our findings highlight the technological engineering singlet and triplet excitons using different kinds of host-vip interactions based on their electronic characteristics.
