We report that a novel exciton feedback effect is observed by introducing the bis（2-methyl-8-quinolinolato）（4- phenylphenolato）Muminum （BAlq） inserted between the emitting layer （EML） and the electron transpor...We report that a novel exciton feedback effect is observed by introducing the bis（2-methyl-8-quinolinolato）（4- phenylphenolato）Muminum （BAlq） inserted between the emitting layer （EML） and the electron transporting layer in blue organic light emitting diodes. As an exciton feedback layer （EFL）, the BAlq does not act as a traditional hole blocking effect. The design of this kind of device structure can greatly reduce excitons＇ quenching due to accumulated space charge at the exciton formation interface. Meanwhile, the non-radiative energy transfer from EFL to the EML can also be utilized to enhance the excitons＇ formation, which is confirmed by the test of photolumimescent transient lifetime decay and electroluminescence enhancement of these devices. Accordingly, the optimal device presents the improved performances with the maximum current efficiency of 4.2 cd/A and the luminance of 24600cd/m2, which are about 1.45 times and 1.75 times higher than those of device A （control device） without the EFL, respectively. Simultaneously, the device shows an excellent color stability with a tiny offset of the CIE coordinates （△x = ±0.003, △y = ±0.004） and a relatively lower efficiency roll-off of 26.2% under the driving voltage varying from 3 V to 10 V.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 cyclometalated greenish-yellow emitter 2,3-diphenylimidazo[1,2-a]pyridine iridium（Ill） complex is successfully synthesized and used to fabricate phosphorescent organic light-emitting diodes. The optimized device e...A cyclometalated greenish-yellow emitter 2,3-diphenylimidazo[1,2-a]pyridine iridium（Ill） complex is successfully synthesized and used to fabricate phosphorescent organic light-emitting diodes. The optimized device exhibits a greenish-yellow emission with the peak at 523nm and a strong shoulder at 557nm, corresponding to Commission Internationale de l＇Eclairage coordinates of （0.38, 0.68）. The full width at half maximum of the device is 93 nm, which is broader than the fac-tris（2-phenylpyridine）iridium [Ir（ppy）3] based reference device of 78 nm. Meanwhile, a maximum current efficiency of 62.6 cd/A （47.51m/W） is obtained. This result is higher than a maximum current efficiency of 54.8 cd/A （431m/W） of the Ir（ppy）a based device. The results indicate that this new iridium complex may have potential applications in fabricating high color rendering index white organic light emitting diodes.展开更多
Through experiments and computer simulation,the influence of the energy levels of organic materials and electrode materials in the organic light-emitting diodes (OLEDs) on the device performances is discussed.Results ...Through experiments and computer simulation,the influence of the energy levels of organic materials and electrode materials in the organic light-emitting diodes (OLEDs) on the device performances is discussed.Results show that the device performances are influenced by not only the carrier injection barriers at the electrode interface but also the barriers at the organic heterojunction interface.This result is helpful to the selection of the organic materials and their arrangement in the optimal design of OLEDs.展开更多
Graphene-based flexible transparent electrodes(FTEs)are promising candidate materials for developing next-generation flexible organic light-emitting diodes(OLEDs).However,the quest for high-efficiency OLEDs is hindere...Graphene-based flexible transparent electrodes(FTEs)are promising candidate materials for developing next-generation flexible organic light-emitting diodes(OLEDs).However,the quest for high-efficiency OLEDs is hindered by the low light-extraction and charge injection efficiencies of graphene electrode.Here,we combine the frustrated Lewis pair doping with nanostructure engineering to obtain high-performance graphene FTE.A p-type dopant aci-nitromethane-tris(pentafluorophenyl)borane(ANBCF)was synthesized and deposited on graphene FTE to form an aperiodic nanostructure,which not only improves the light-extraction but also stably p-dopes graphene to enhance its hole injection.The use of ANBCF-doped graphene as the anode enables high-efficiency flexible green OLEDs with external quantum efficiency(EQE)and power efficiency(PE)out-performing most flexible graphene OLEDs of comparable structure.This study provides a simple and effective pathway to fabricate high-performance graphene FTEs for efficient flexible OLEDs.展开更多
Nanorod-like TiO2 (nc-TiO2) and MoO3 (nc-MoO3) films were thermally grown from Ti- and Mo-metallic wafers. Nanohybrid films of N,N’-diphenyl-N,N’-bis(1-naphthyl)(1,1’-biphenyl)-4,4’diamine (NPB)/TiO2 and NPB/MoO3 ...Nanorod-like TiO2 (nc-TiO2) and MoO3 (nc-MoO3) films were thermally grown from Ti- and Mo-metallic wafers. Nanohybrid films of N,N’-diphenyl-N,N’-bis(1-naphthyl)(1,1’-biphenyl)-4,4’diamine (NPB)/TiO2 and NPB/MoO3 used as anode/hole transport layer (HTL) heterojunctions in blue organic light emission diodes (OLEDs) were prepared by coating NPB onto the nc-TiO2 and nc-MoO3 and TiO2. Characterization of the nanostructured hybrid layers showed that both the photoluminescent property and current-voltage (I-V) characteristics of the hybrid materials were significantly enhanced in comparison with the standard NPB polymer. The electroluminous efficiency of the hybrid devices was considerably enhanced in comparison with the standard device. This suggests a useful application for fabricating “reverse” OLEDs, where the emission light goes-out through the semitransparent cathode, instead of the indium tin oxide (ITO) anode. For this, the ohmic contacts of conducting wires to metallic electrodes can be made much better than to ITO anodes.展开更多
In this Letter, blue phosphorescence organic light-emitting diodes （PHOLEDs） employ structures for electron and/or hole confinement; 1,3,5-tris（N-phenylbenzimiazole-2-yl）benzene is used as a hole confinement layer...In this Letter, blue phosphorescence organic light-emitting diodes （PHOLEDs） employ structures for electron and/or hole confinement; 1,3,5-tris（N-phenylbenzimiazole-2-yl）benzene is used as a hole confinement layer and tris-（phenylpyrazole）iridium [Ir（ppz）3] is utilized for an electron confinement layer （ECL）. The electrical and optical properties of the fabricated blue PHOLEDs with various carrier-confinement structures are analyzed. Structures with a large ehergy offset between the carrier confinement and emitting layers enhance the charge-carrier balance in the emitting region, resulting from the effective carrier confinement. The maximum external quantum efficiency of the blue PHOLEDs with the double-ECLs is 24.02% at 1500 cd/m^2 and its luminous efficiency is 43.76 cd/A, which is 70.47% improved compared to the device without a carrier-confinement layer.展开更多
Red and near-infrared(NIR)organic light-emitting diodes(OLED)have gained remarkable interest due to their numerous applications.However,the construction of highly emissive emitters is hampered by the energy-gap law an...Red and near-infrared(NIR)organic light-emitting diodes(OLED)have gained remarkable interest due to their numerous applications.However,the construction of highly emissive emitters is hampered by the energy-gap law and aggregation-caused quenching(ACQ)effect.Whereas,aggregationinduced emission(AIE)materials could avoid the undesirable ACQ effect and emit bright light in aggregated state,which is one class of the most promising materials to fabricate high-performance OLED with a high external quantum efficiency and low efficiency roll-off.This review summarizes recent advances in red and NIR OLED with AIE property,including the traditional fluorescence,thermally activated delayed fluorescence,and hybridized local and charge transfer compounds.Meanwhile,the emphasis attention is paid to the molecular design principles,as well as the molecular structure-photophysical characteristics.We also briefly further outlook the challenges and perspective of red and NIR AIE luminogens.展开更多
The electronic structures and spectroscopic properties of heteroleptic cyclometalated iridium（Ⅲ） complexes were investigated. The geometries, electronic structures, and the lowest-lying excited states of （DBQ）2Ir...The electronic structures and spectroscopic properties of heteroleptic cyclometalated iridium（Ⅲ） complexes were investigated. The geometries, electronic structures, and the lowest-lying excited states of （DBQ）2Ir（acac） and （MDQ）2Ir（acac） were investigated via density functional theory-based approaches. A series of designed models of （DBQ）2Ir（dpis）, （DBQ）2Ir（tpip）, （MDQ）2Ir（dpis） and （MDQ）2Ir（tpip） was also calculated for comparison. The structures in the ground and excited states were optimized via B3LYP method. The lowest absorptions and emissions spectra were evaluated via TD-B3LYP and TD-PBE1PBE methods, The computational results reveal that the emission peaks of the designed complexes are at around 585-640 nm, which belong to the orange-yellow wavelength. The frontier molecular orbital properties indicate that the Ir（Ⅲ） complexes have low efficiency roll-off.展开更多
基金Supported by the National Natural Science Foundation of China under Grant No 60906022the Natural Science Foundation of Tianjin under Grant No 10JCYBJC01100+1 种基金the Scientific Developing Foundation of Tianjin Education Commission under Grant No 2011ZD02the Key Science and Technology Support Program of Tianjin under Grant No 14ZCZDGX00006
文摘We report that a novel exciton feedback effect is observed by introducing the bis（2-methyl-8-quinolinolato）（4- phenylphenolato）Muminum （BAlq） inserted between the emitting layer （EML） and the electron transporting layer in blue organic light emitting diodes. As an exciton feedback layer （EFL）, the BAlq does not act as a traditional hole blocking effect. The design of this kind of device structure can greatly reduce excitons＇ quenching due to accumulated space charge at the exciton formation interface. Meanwhile, the non-radiative energy transfer from EFL to the EML can also be utilized to enhance the excitons＇ formation, which is confirmed by the test of photolumimescent transient lifetime decay and electroluminescence enhancement of these devices. Accordingly, the optimal device presents the improved performances with the maximum current efficiency of 4.2 cd/A and the luminance of 24600cd/m2, which are about 1.45 times and 1.75 times higher than those of device A （control device） without the EFL, respectively. Simultaneously, the device shows an excellent color stability with a tiny offset of the CIE coordinates （△x = ±0.003, △y = ±0.004） and a relatively lower efficiency roll-off of 26.2% under the driving voltage varying from 3 V to 10 V.
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.
文摘A cyclometalated greenish-yellow emitter 2,3-diphenylimidazo[1,2-a]pyridine iridium（Ill） complex is successfully synthesized and used to fabricate phosphorescent organic light-emitting diodes. The optimized device exhibits a greenish-yellow emission with the peak at 523nm and a strong shoulder at 557nm, corresponding to Commission Internationale de l＇Eclairage coordinates of （0.38, 0.68）. The full width at half maximum of the device is 93 nm, which is broader than the fac-tris（2-phenylpyridine）iridium [Ir（ppy）3] based reference device of 78 nm. Meanwhile, a maximum current efficiency of 62.6 cd/A （47.51m/W） is obtained. This result is higher than a maximum current efficiency of 54.8 cd/A （431m/W） of the Ir（ppy）a based device. The results indicate that this new iridium complex may have potential applications in fabricating high color rendering index white organic light emitting diodes.
文摘Through experiments and computer simulation,the influence of the energy levels of organic materials and electrode materials in the organic light-emitting diodes (OLEDs) on the device performances is discussed.Results show that the device performances are influenced by not only the carrier injection barriers at the electrode interface but also the barriers at the organic heterojunction interface.This result is helpful to the selection of the organic materials and their arrangement in the optimal design of OLEDs.
基金supported by the National Science Foundation of China(Nos.52272051,52172057,52188101 and 52002375)Ministry of Science and Technology of China(No.2021YFA1200804)+3 种基金Chinese Academy of Sciences(Nos.ZDBSLYJSC027 and XDB30000000)Postdoctoral Science Foundation of China(Nos.2020M670812 and 2020TQ0328)Liaoning Revitalization Talents Program(No.XLYC1808013)Guangdong Basic and Applied Basic Research Foundation(No.2020B0301030002).
文摘Graphene-based flexible transparent electrodes(FTEs)are promising candidate materials for developing next-generation flexible organic light-emitting diodes(OLEDs).However,the quest for high-efficiency OLEDs is hindered by the low light-extraction and charge injection efficiencies of graphene electrode.Here,we combine the frustrated Lewis pair doping with nanostructure engineering to obtain high-performance graphene FTE.A p-type dopant aci-nitromethane-tris(pentafluorophenyl)borane(ANBCF)was synthesized and deposited on graphene FTE to form an aperiodic nanostructure,which not only improves the light-extraction but also stably p-dopes graphene to enhance its hole injection.The use of ANBCF-doped graphene as the anode enables high-efficiency flexible green OLEDs with external quantum efficiency(EQE)and power efficiency(PE)out-performing most flexible graphene OLEDs of comparable structure.This study provides a simple and effective pathway to fabricate high-performance graphene FTEs for efficient flexible OLEDs.
文摘Nanorod-like TiO2 (nc-TiO2) and MoO3 (nc-MoO3) films were thermally grown from Ti- and Mo-metallic wafers. Nanohybrid films of N,N’-diphenyl-N,N’-bis(1-naphthyl)(1,1’-biphenyl)-4,4’diamine (NPB)/TiO2 and NPB/MoO3 used as anode/hole transport layer (HTL) heterojunctions in blue organic light emission diodes (OLEDs) were prepared by coating NPB onto the nc-TiO2 and nc-MoO3 and TiO2. Characterization of the nanostructured hybrid layers showed that both the photoluminescent property and current-voltage (I-V) characteristics of the hybrid materials were significantly enhanced in comparison with the standard NPB polymer. The electroluminous efficiency of the hybrid devices was considerably enhanced in comparison with the standard device. This suggests a useful application for fabricating “reverse” OLEDs, where the emission light goes-out through the semitransparent cathode, instead of the indium tin oxide (ITO) anode. For this, the ohmic contacts of conducting wires to metallic electrodes can be made much better than to ITO anodes.
文摘In this Letter, blue phosphorescence organic light-emitting diodes （PHOLEDs） employ structures for electron and/or hole confinement; 1,3,5-tris（N-phenylbenzimiazole-2-yl）benzene is used as a hole confinement layer and tris-（phenylpyrazole）iridium [Ir（ppz）3] is utilized for an electron confinement layer （ECL）. The electrical and optical properties of the fabricated blue PHOLEDs with various carrier-confinement structures are analyzed. Structures with a large ehergy offset between the carrier confinement and emitting layers enhance the charge-carrier balance in the emitting region, resulting from the effective carrier confinement. The maximum external quantum efficiency of the blue PHOLEDs with the double-ECLs is 24.02% at 1500 cd/m^2 and its luminous efficiency is 43.76 cd/A, which is 70.47% improved compared to the device without a carrier-confinement layer.
基金supported by the National Natural Science Foundation of China(no.21905198)the Open Fund of Guangdong Provincial Key Laboratory of Luminescence from Molecular Aggregates,Guangzhou 510640,China(South China University of Technology),and the starting grants of Tianjin University and Tianjin Government.
文摘Red and near-infrared(NIR)organic light-emitting diodes(OLED)have gained remarkable interest due to their numerous applications.However,the construction of highly emissive emitters is hampered by the energy-gap law and aggregation-caused quenching(ACQ)effect.Whereas,aggregationinduced emission(AIE)materials could avoid the undesirable ACQ effect and emit bright light in aggregated state,which is one class of the most promising materials to fabricate high-performance OLED with a high external quantum efficiency and low efficiency roll-off.This review summarizes recent advances in red and NIR OLED with AIE property,including the traditional fluorescence,thermally activated delayed fluorescence,and hybridized local and charge transfer compounds.Meanwhile,the emphasis attention is paid to the molecular design principles,as well as the molecular structure-photophysical characteristics.We also briefly further outlook the challenges and perspective of red and NIR AIE luminogens.
基金Supported by the National Natural Science Foundation for Creative Research Group, China（No.21003057）, the China Post- doctoral Science Foundation（No.2013M541286） and the Science and Technology Planning Project of Jilin Province, China（Nos. 20101512, 20110320, 201201078, 20140520109JH and 20150414003GH）.
文摘The electronic structures and spectroscopic properties of heteroleptic cyclometalated iridium（Ⅲ） complexes were investigated. The geometries, electronic structures, and the lowest-lying excited states of （DBQ）2Ir（acac） and （MDQ）2Ir（acac） were investigated via density functional theory-based approaches. A series of designed models of （DBQ）2Ir（dpis）, （DBQ）2Ir（tpip）, （MDQ）2Ir（dpis） and （MDQ）2Ir（tpip） was also calculated for comparison. The structures in the ground and excited states were optimized via B3LYP method. The lowest absorptions and emissions spectra were evaluated via TD-B3LYP and TD-PBE1PBE methods, The computational results reveal that the emission peaks of the designed complexes are at around 585-640 nm, which belong to the orange-yellow wavelength. The frontier molecular orbital properties indicate that the Ir（Ⅲ） complexes have low efficiency roll-off.
