Single-emitter white organic light-emitting diode(WOLED) based on small organic molecule exhibits great potential in simplifying fabrication process of WOLEDs. However, the design and synthesis of molecule for highly ...Single-emitter white organic light-emitting diode(WOLED) based on small organic molecule exhibits great potential in simplifying fabrication process of WOLEDs. However, the design and synthesis of molecule for highly efficient single-emitter WOLED still remains a challenge. Herein, two asymmetric donor-acceptor-acceptor'(D-A-A') type molecule(PTZ-PQ-F and PTZ-PQ-CF3) are developed by employing trifluoromethyl(CF_(3)) or fluorine atom as secondary acceptor, which can exhibit white lighting with dual emission bands consisting of blue traditional fluorescence from quasi-axial(ax) conformer and orange thermally activated delayed fluorescence(TADF) from quasi-equatorial(eq) conformer. The introduction of CF_(3) into PTZ-PQ-CF3 greatly enhanced the photoluminescence quantum yield(PLQY) by suppressing the nonradiative deactivation. Owing to electron-inductive-effect of CF3, the “eq” conformer of PTZ-PQCF3 exhibits a much smaller ΔESTof 0.01 e V to realize more efficient reverse intersystem crossing(RISC)process, and then enhance the exciton utilization(nearly 100%) of the whole dual emission system. Consequently, single-emitter WOLEDs based on PTZ-PQ-CF3 show nearly standard white emission with EQE of 13.0% and CIE of(0.35, 0.36) in m CP host and show warm white emission with high EQE of 25.5%and CIE of(0.40, 0.47) in 35 Dcz PPy host, which are the best performance among reported single-emitter WOLEDs.展开更多
The efficiency of organic light-emitting devices （OLEDs） based on N,N＇-bis（1-naphthyl）-N,N＇-diphenyl-N,1＇- biphenyl-4,4＇-diamine （NPB） （the hole transport layer） and tris（8-hydroxyquinoline） aluminum （A...The efficiency of organic light-emitting devices （OLEDs） based on N,N＇-bis（1-naphthyl）-N,N＇-diphenyl-N,1＇- biphenyl-4,4＇-diamine （NPB） （the hole transport layer） and tris（8-hydroxyquinoline） aluminum （Alq3） （both emission and electron transport layers） is improved remarkably by inserting a LiF interlayer into the hole transport layer. This thin LiF interlayer can effectively influence electrical performance and significantly improve the current efficiency of the device. A device with an optimum LiF layer thickness at the optimum position in NPB exhibits a maximum current efficiency of 5.96 cd/A at 215.79 mA/cm2, which is about 86% higher than that of an ordinary device （without a LiF interlayer, 3.2 cd/A）. An explanation can be put forward that LiF in the NPB layer can block holes and balance the recombination of holes and electrons. The results may provide some valuable references for improving OLED current efficiency.展开更多
Fluorescence/phosphorescence hybrid white organic light-emitting devices（WOLEDs） based on double emitting layers（EMLs） with high color stability are fabricated.The simplified EMLs consist of a non-doped blue therm...Fluorescence/phosphorescence hybrid white organic light-emitting devices（WOLEDs） based on double emitting layers（EMLs） with high color stability are fabricated.The simplified EMLs consist of a non-doped blue thermally activated delayed fluorescence（TADF） layer using 9,9-dimethyl-9,10-dihydroacridine-diphenylsulfone（DMAC-DPS） and an ultrathin non-doped yellow phosphorescence layer employing bis[2-（4-tertbutylphenyl）benzothiazolato-N,C2＇]iridium（acetylacetonate）（（tbt）_2Ir（acac））.Two kinds of materials of 4,7-diphenyl-1,10-phenanthroline（Bphen） and 1,3,5-tris（2-Nphenylbenzimidazolyl） benzene（TPBi） are selected as the electron transporting layer（ETL）,and the thickness of yellow EML is adjusted to optimize device performance.The device based on a 0.3-nm-thick yellow EML and Bphen exhibits high color stability with a slight Commission International de l＇Eclairage（CIE） coordinates variation of（0.017,0.009） at a luminance ranging from 52 cd/m^2 to 6998 cd/m^2.The TPBi-based device yields a high efficiency with a maximum external quantum efficiency（EQE）,current efficiency,and power efficiency of 10%,21.1 cd/A,and 21.3 lm/W,respectively.The ultrathin yellow EML suppresses hole trapping and short-radius Dexter energy transfer,so that Forster energy transfer（FRET）from DMAC-DPS to（tbt）_2Ir（acac） is dominant,which is beneficial to keep the color stable.The employment of TPBi with higher triplet excited state effectively alleviates the triplet exciton quenching by ETL to improve device efficiency.展开更多
A numerical model of multilayer organic light-emitting devices is presented in this article. This model is based on the drift-diffusion equations which include charge injection, transport, space charge effects, trappi...A numerical model of multilayer organic light-emitting devices is presented in this article. This model is based on the drift-diffusion equations which include charge injection, transport, space charge effects, trapping, heterojunction interface and recombination process. The device structure in the simulation is ITO/CuPc （20 nm）/NPD （40 nm）/Alq3 （60 nm）/LiF/Al. There are two heterojunctions which should be dealt with in the simulation. The I-V characteristics, carrier distribution and recombination rate of a device are calculated. The simulation results and measured data are in good agreement.展开更多
High performance organic light-emitting devices （OLEDs） have been investigated by using fluorescent bis （2-methyl-8-quinolinolato）（para-phenylphenolato）aluminum（BAlq） as an emissive layer on the performance of...High performance organic light-emitting devices （OLEDs） have been investigated by using fluorescent bis （2-methyl-8-quinolinolato）（para-phenylphenolato）aluminum（BAlq） as an emissive layer on the performance of multicolor devices consisting of N, N＇-bis-（1-naphthyl）-N,N＇diphenyl- 1,1＇-biphenyl-4,4＇- diamine （NPB） as hole transport layer. The results show that the performance of heterostructure blue light-emitting device composed of 8-hydroxyquinoline aluminum （Alq3） as an electron transport layer has been dramatically enhanced. In the case of high performance heterostructure devices, the electroluminescent spectra has been perceived to vary strongly with the thickness of the organic layers due to the different recombination region, which indicates that various color devices composed of identical components could be implemented by changing the film thickness of different functional layers.展开更多
We investigate the electron injection effect of inserting a thin aluminum（Al） layer into cesium carbonate（Cs2CO3）injection layer. Two groups of organic light-emitting devices（OLEDs） are fabricated. For the first...We investigate the electron injection effect of inserting a thin aluminum（Al） layer into cesium carbonate（Cs2CO3）injection layer. Two groups of organic light-emitting devices（OLEDs） are fabricated. For the first group of devices based on Alq3, we insert a thin Al layer of different thickness into Cs2CO3 injection layer, and the device＇s maximum current efficiency of 6.5 cd/A is obtained when the thickness of the thin Al layer is 0.4 nm. However, when the thickness of Al layer is 0.8 nm, the capacity of electron injection is the strongest. To validate the universality of this approach, then we fabricate another group of devices based on another blue emitting material. The maximum current efficiency of the device without and with a thin Al layer is 4.51 cd/A and 4.84 cd/A, respectively. Inserting a thin Al layer of an appropriate thickness into Cs2CO3 layer can result in the reduction of electron injection barrier, enhancement of the electron injection, and improvement of the performance of OLEDs. This can be attributed to the mechanism that thermally evaporated Cs2CO3 decomposes into cesium oxides, the thin Al layer reacts with cesium oxides to form Al–O–Cs complex, and the amount of the Al–O–Cs complex can be controlled by adjusting the thickness of the thin Al layer.展开更多
A bilayer model with ohmic anode contact and injection limited cathode contact has been proposed to calculate the recombination efficiency and recombination zone width of the device. The effects of the thickness of ho...A bilayer model with ohmic anode contact and injection limited cathode contact has been proposed to calculate the recombination efficiency and recombination zone width of the device. The effects of the thickness of hole transport layer and the barriers of organic/organic interface on the combination efficiency and recombination width have been discussed. It is found that： （1） When the electrons are blocked fully and the holes are not blocked significantly at the organic/organic interface, for a given Lh/L, the recombination efficiency increases with increasing the applied voltage, but at a higher applied voltage, the recombination efficiency decreases with increasing Lh/L; （2） The recombination efficiency increases with increasing applied voltage and Hh＇, and when applied voltage and Hh＇ exceed some value, the recombination efficiency appears as a plateau; （3） The recombination width decreases with increasing the applied voltage and Lh/L. This model might explain the relative experiment phenomena.展开更多
Here,this work presents an air-stable ultrabright inverted organic lightemitting device(OLED)by using zinc ionchelated polyethylenimine(PEI)as electron injection layer.The zinc chelation is demonstrated to increase th...Here,this work presents an air-stable ultrabright inverted organic lightemitting device(OLED)by using zinc ionchelated polyethylenimine(PEI)as electron injection layer.The zinc chelation is demonstrated to increase the conductivity of the PEI by three orders of magnitude and passivate the polar amine groups.With these physicochemical properties,the inverted OLED shows a record-high external quantum efficiency of 10.0% at a high brightness of 45,610 cd m^(-2) and can deliver a maximum brightness of 121,865 cd m^(-2).Besides,the inverted OLED is also demonstrated to possess an excellent air stability(humidity,35%)with a half-brightness operating time of 541 h@1000 cd m^(-2) without any protection nor encapsulation.展开更多
The dependence of the performance of organic light-emitting devices（OLEDs） on the sheet resistance of indiumtin-oxide（ITO） anodes was investigated by measuring the steady state current density brightness voltage c...The dependence of the performance of organic light-emitting devices（OLEDs） on the sheet resistance of indiumtin-oxide（ITO） anodes was investigated by measuring the steady state current density brightness voltage characteristics and the electroluminescent spectra. The device with a higher sheet resistance anode shows a lower current density, a lower brightness level, and a higher operation voltage. The electroluminescence（EL） efficiencies of the devices with the same structure but different ITO anodes show more complicated differences. Furthermore, the shift of the light-emitting zone toward the anode was found when an anode with a higher sheet resistance was used. These performance differences are discussed and attributed to the reduction of hole injection and the increase in voltage drop over ITO anode with the increase in sheet resistance.展开更多
This paper reports that the doped bi-layer organic light-emitting devices are fabricated by doping in different regions of the light-emitting layer, the admittance and luminance spectra to characterize the capacitance...This paper reports that the doped bi-layer organic light-emitting devices are fabricated by doping in different regions of the light-emitting layer, the admittance and luminance spectra to characterize the capacitance and luminance of the device are measured. Negative capacitance （NC） appeared at low frequencies when the doped devices are biased with high voltages. The measured phase difference between AC voltage applied across the device and AC current flowing through the device show that the device is inductive when NC appears.展开更多
In this paper we report on a high-contrast top-emitting organic light-emitting device utilizing a moderate-reflection contrast-enhancement stack and a high refractive index anti-reflection layer.The contrast-enhanceme...In this paper we report on a high-contrast top-emitting organic light-emitting device utilizing a moderate-reflection contrast-enhancement stack and a high refractive index anti-reflection layer.The contrast-enhancement stack consists of a thin metal anode layer,a dielectric bilayer,and a thick metal underlayer.The resulting device,with the optimized contrast-enhancement stack thicknesses of Ni（30 nm）/MgF 2（62 nm）/ZnS（16 nm）/Ni（20 nm） and the 25-nm-thick ZnS anti-reflection layer,achieves a luminous reflectance of 4.01% in the visible region and a maximum current efficiency of 0.99 cd/A（at 62.3 mA/cm 2） together with a very stable chromaticity.The contrast ratio reaches 561：1 at an on-state brightness of 1000 cd/m^2 under an ambient illumination of 140 lx.In addition,the anti-reflection layer can also enhance the transmissivity of the cathode and improve light out-coupling by the effective restraint of microcavity effects.展开更多
A new structure containing negative refractive index dielectric layer（NRlDL） is introduced into microcavity. The properties of the new mierocavity organic light-emitting devices（MOLEDs） are investigated. In the ex...A new structure containing negative refractive index dielectric layer（NRlDL） is introduced into microcavity. The properties of the new mierocavity organic light-emitting devices（MOLEDs） are investigated. In the experiment, the transfer matrix method is adopted. The dependence of reflectance and transmittance on the refractive index and thickness of NRIDL are analyzed in detail. Compared with the electroluminescence spectra of non-NRIDL diodes, the line widths of the spectra of the MOLEDs are narrower and all the peaks enhance. The results show that the new structure is beneficial to improve the performance and reduce the thickness of microcavity devices.展开更多
A triple layer organic light-emitting diode (OLED) with two heterostructure of indium-tin oxide (ITO)/N,N’-diphenyl-N, N’-bis(1-naphthyl) (1,1’-biphenyl)-4,4’-diamine (NPB)/2,9-dimethyl-4,7-diphenyl-1,10-phenanthr...A triple layer organic light-emitting diode (OLED) with two heterostructure of indium-tin oxide (ITO)/N,N’-diphenyl-N, N’-bis(1-naphthyl) (1,1’-biphenyl)-4,4’-diamine (NPB)/2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP)/ 8-Hydrox- yquinoline aluminum (Alq3)/Mg:Ag has been fabricated by using the vacuum deposition method. The influence of different film thickness of BCP layer on the performance of the OLEDs has been investigated. The results show that when the thickness of the BCP layer film gradually r...展开更多
We chose pentacene as a hole injection layer（HIL） to fabricate the high performance blue fluorescent organic lightemitting devices（OLEDs）. We found that the carrier mobility of the pentacene thin films could be ef...We chose pentacene as a hole injection layer（HIL） to fabricate the high performance blue fluorescent organic lightemitting devices（OLEDs）. We found that the carrier mobility of the pentacene thin films could be efficiently improved after a critical annealing at temperature 120℃. Then we performed the tests of scanning electron microscopy, atomic force microscopy, and Kelvin probe to explore the effect of annealing on the pentacene films. The pentacene film exhibited a more crystalline form with better continuities and smoothness after annealing. The optimal device with 120℃ annealed pentacene film and n-doped electron transport layer（ETL） presents a low turn-on voltage of 2.6 V and a highest luminance of 134800 cd/m^2 at 12 V, which are reduced by 26% and improved by 50% compared with those of the control device.展开更多
A binary-mixed electron transport layer(ETL)has been reported for constructing solution-processable near-infrared organic light-emitting diodes(NIR OLEDs).Relative to the single-component ETL,the binarymixed ETL compo...A binary-mixed electron transport layer(ETL)has been reported for constructing solution-processable near-infrared organic light-emitting diodes(NIR OLEDs).Relative to the single-component ETL,the binarymixed ETL composed of PDINN:TPBi can enhance the carrier transport capacity,reduce device impedance,and weaken fiuorescence quenching of the emitting layer.By carefully selecting an appropriate luminescent material Y5(a nonfullerene electron acceptor in organic solar cells)and precisely fine-tuning the molecular aggregation in active layer using a mixed solvent,the morphology is optimized and luminescence performance is enhanced,resulting in efficient NIR OLEDs with an emission peak at 890 nm.The experiment showcases a Y5-based near-infrared OLED with a maximum radiance of 34.9 W sr^(-1)m^(-2)and a maximum external quantum efficiency of 0.50%,which is among the highest values reported for nondoped fiuorescent NIR OLEDs with an emission peak over 850 nm.展开更多
Triphenylamine(TPA)is the most promising donor fragment for the construction of long-wavelength thermally activated delayed fluorescence(TADF)emitters owing to its suitable dihedral angle that could enhance radiative ...Triphenylamine(TPA)is the most promising donor fragment for the construction of long-wavelength thermally activated delayed fluorescence(TADF)emitters owing to its suitable dihedral angle that could enhance radiative decay to compete with the serious non-radiative decay.However,the moderate electron-donating capacity of TPA seriously limits the selection of acceptor for constructing longwavelength TADF emitters with narrow bandgaps.To address this issue,in this work,the peripheral benzene of TPA was replaced with 1,4-benzodioxane and anisole to obtain two new electrondonating units N-(2,3-dihydrobenzo[b][1,4]dioxin-6-yl)-N-phenyl-2,3-dihydrobenzo[b][1,4]dioxin-6-amine(TPADBO,−5.02 eV)and 4-methoxy-N-(4-methoxyphenyl)-N-phenylaniline(TPAMO,−5.00 eV),which possess much shallower highest occupied molecule orbital(HOMO)energy levels than the prototype TPA(−5.33 eV).Based on TPA and the modified TPA donor fragments,three TADF emitters were designed and synthesized,namely Py-TPA,Py-TPADBO and Py-TPAMO,with the same acceptor fragment 12-(2,6-diisopropylphenyl)pyrido[2′,3′:5,6]pyrazino[2,3-f][1,10]phenanthroline(Py).Among them,Py-TPAMO exhibits the highest photoluminescence quantum yield of 78.4%and the smallest singlet-triplet energy gap,which is because the introduction of anisole does not cause significant molecule deformation for the excited Py-TPAMO.And Py-TPAMO-based OLEDs successfully realize a maximum external quantum efficiency of 25.5%with the emission peak at 605 nm.This work provides a series of candidate of donor fragments for the development of efficient long-wavelength TADF emitters.展开更多
The growing environmental concerns regarding rare earth elements in fluorescent powders,along with high production costs,have increased the demand for sustainable alternatives.We propose a promising solution using lum...The growing environmental concerns regarding rare earth elements in fluorescent powders,along with high production costs,have increased the demand for sustainable alternatives.We propose a promising solution using luminescent metal-organic frameworks(LMOFs)with large surface areas and tunable pore structures,combined with organic carbon quantum dots(CQDs).This study develops a novel white lightemitting diode(WLED)fluorescent powder by incorporating yellow-fluorescent quantum dots(CQDs-Y)into blue-emitting LMOF(ZJU-28),forming the composite material CQDs-Y-n@ZJU-28.The composite exhibits excellent thermal and chemical stability,long-term storage performance,and emits warm white light(CIE:0.3277,0.3281)when subjected to excitation at 365 nm,along with an external quantum efficiency(EQE)of 8.85%.Furthermore,it exhibits tunable emission characteristics and promising LED performance,showcasing a color rendering index(CRI)of 78 and a correlated color temperature of 3384 K.The emitted light undergoes minimal deviation in color towards the white end of the spectrum in the temperature range of 277-437 K,making it an ideal candidate for advanced WLED applications.展开更多
A novel bipolar host tris(4-(pyrimidin-5-yl)phenyl)amine(TPMTPA) constructed by incorporating triphenylamine as the electron-donating core and pyrimidine as the electron-accepting peripheries was designed and synthesi...A novel bipolar host tris(4-(pyrimidin-5-yl)phenyl)amine(TPMTPA) constructed by incorporating triphenylamine as the electron-donating core and pyrimidine as the electron-accepting peripheries was designed and synthesized.TPMTPA achieves excellent bipolar charge transport properties and has high enough triplet energy level to sensitize green,yellow,orange,red and deep-red phosphors.By using TPMTPA as a host,high performance green,yellow,orange,red and deep-red phosphorescent organic light-emitting devices(PhOLEDs) were demonstrated with maximum external quantum efficiencies of 20.4%,17.6%,15.1%,15.3%and 15.7%respectively.These results suggested that TPMTPA is a versatile high performance host for PhOLEDs of different emission colors.展开更多
Highly efficient stacked organic light-emitting devices (OLEDs) have been fabricated using Mg:Alq3:BCP/ WO3 as a novel intermediate layer, which connects two identical emissive units. The stacked OLEDs consisting of N...Highly efficient stacked organic light-emitting devices (OLEDs) have been fabricated using Mg:Alq3:BCP/ WO3 as a novel intermediate layer, which connects two identical emissive units. The stacked OLEDs consisting of NPB/Alq3 exhibited high current efficiency and brightness characteristics over conven- tional single-unit device. At 200 mA/cm2, the current efficiency of the stacked OLEDs using the inter- mediate layers of Mg:Alq3:BCP/WO3 were about 6.85 cd/A, doubling that of the conventional device. The results may prove the method to be effective to enhance the current efficiency and brightness of OLEDs.展开更多
In this article, we reported the synthesis and characterization of a novel silafluorene-based host material, 1,3-bis（5-methyl-5H- dibenzo[b,d]silol-5-yl）benzene （Me-DBSiB）, for blue phosphorescent organic light-em...In this article, we reported the synthesis and characterization of a novel silafluorene-based host material, 1,3-bis（5-methyl-5H- dibenzo[b,d]silol-5-yl）benzene （Me-DBSiB）, for blue phosphorescent organic light-emitting devices （PHOLEDs）. The Me- DBSiB was constructed by linking 9-methyl-9-silafluorene units to the phenyl framework through the sp3-hybridized silica atom to maintain high singlet and triplet energy, as well as to enhance thermal and photo-stability. The calculated result shows that the phenyl core does not contribute to both the highest occupied molecular orbital and lowest unoccupied molecular orbital. Wide optical energy gap of 4.1 eV was achieved. When the Me-DBSiB was used as the host and iridium （Ⅲ） bis[（4,6-difluorophenyl）pyridinato-N,C2＇]picolate （Firpic） as the vip, a maximum current efficiency was 14.8 cd/A, lower than the counterpart of 1,3-bis（9-carbazolyl）benzene （28 cd/A）. The unbalanced barrier for electron and hole injection to host layer may be responsible for low efficiency. Even so, our results show that silafluorene moieties are promising building blocks for constructing wide-energy-gap host materials.展开更多
基金the supports by the National Natural Science Foundation of China (No.22175049)the Opening Project of Key Laboratory of Optoelectronic Chemical Materials and Devices of Ministry of Education,Jianghan University (No.JDGD-202213)the support of the Fundamental Research Funds for the Central Universities (Harbin Institute of Technology)。
文摘Single-emitter white organic light-emitting diode(WOLED) based on small organic molecule exhibits great potential in simplifying fabrication process of WOLEDs. However, the design and synthesis of molecule for highly efficient single-emitter WOLED still remains a challenge. Herein, two asymmetric donor-acceptor-acceptor'(D-A-A') type molecule(PTZ-PQ-F and PTZ-PQ-CF3) are developed by employing trifluoromethyl(CF_(3)) or fluorine atom as secondary acceptor, which can exhibit white lighting with dual emission bands consisting of blue traditional fluorescence from quasi-axial(ax) conformer and orange thermally activated delayed fluorescence(TADF) from quasi-equatorial(eq) conformer. The introduction of CF_(3) into PTZ-PQ-CF3 greatly enhanced the photoluminescence quantum yield(PLQY) by suppressing the nonradiative deactivation. Owing to electron-inductive-effect of CF3, the “eq” conformer of PTZ-PQCF3 exhibits a much smaller ΔESTof 0.01 e V to realize more efficient reverse intersystem crossing(RISC)process, and then enhance the exciton utilization(nearly 100%) of the whole dual emission system. Consequently, single-emitter WOLEDs based on PTZ-PQ-CF3 show nearly standard white emission with EQE of 13.0% and CIE of(0.35, 0.36) in m CP host and show warm white emission with high EQE of 25.5%and CIE of(0.40, 0.47) in 35 Dcz PPy host, which are the best performance among reported single-emitter WOLEDs.
基金supported by the National Natural Science Foundation of China (Grant Nos. 60906022 and 60876046)the Tianjin Natural Science Foundation of China (Grant No. 10JCYBJC01100)
文摘The efficiency of organic light-emitting devices （OLEDs） based on N,N＇-bis（1-naphthyl）-N,N＇-diphenyl-N,1＇- biphenyl-4,4＇-diamine （NPB） （the hole transport layer） and tris（8-hydroxyquinoline） aluminum （Alq3） （both emission and electron transport layers） is improved remarkably by inserting a LiF interlayer into the hole transport layer. This thin LiF interlayer can effectively influence electrical performance and significantly improve the current efficiency of the device. A device with an optimum LiF layer thickness at the optimum position in NPB exhibits a maximum current efficiency of 5.96 cd/A at 215.79 mA/cm2, which is about 86% higher than that of an ordinary device （without a LiF interlayer, 3.2 cd/A）. An explanation can be put forward that LiF in the NPB layer can block holes and balance the recombination of holes and electrons. The results may provide some valuable references for improving OLED current efficiency.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61675041 and 61605253)the Foundation for Innovation Research Groups of the National Natural Science Foundation of China(Grant No.61421002)the Science&Technology Department Program of Sichuan Province,China(Grant No.2016HH0027)
文摘Fluorescence/phosphorescence hybrid white organic light-emitting devices（WOLEDs） based on double emitting layers（EMLs） with high color stability are fabricated.The simplified EMLs consist of a non-doped blue thermally activated delayed fluorescence（TADF） layer using 9,9-dimethyl-9,10-dihydroacridine-diphenylsulfone（DMAC-DPS） and an ultrathin non-doped yellow phosphorescence layer employing bis[2-（4-tertbutylphenyl）benzothiazolato-N,C2＇]iridium（acetylacetonate）（（tbt）_2Ir（acac））.Two kinds of materials of 4,7-diphenyl-1,10-phenanthroline（Bphen） and 1,3,5-tris（2-Nphenylbenzimidazolyl） benzene（TPBi） are selected as the electron transporting layer（ETL）,and the thickness of yellow EML is adjusted to optimize device performance.The device based on a 0.3-nm-thick yellow EML and Bphen exhibits high color stability with a slight Commission International de l＇Eclairage（CIE） coordinates variation of（0.017,0.009） at a luminance ranging from 52 cd/m^2 to 6998 cd/m^2.The TPBi-based device yields a high efficiency with a maximum external quantum efficiency（EQE）,current efficiency,and power efficiency of 10%,21.1 cd/A,and 21.3 lm/W,respectively.The ultrathin yellow EML suppresses hole trapping and short-radius Dexter energy transfer,so that Forster energy transfer（FRET）from DMAC-DPS to（tbt）_2Ir（acac） is dominant,which is beneficial to keep the color stable.The employment of TPBi with higher triplet excited state effectively alleviates the triplet exciton quenching by ETL to improve device efficiency.
基金Project supported by Zhejiang Yangguang Cooperation Foundation, China (Grant No W050317)
文摘A numerical model of multilayer organic light-emitting devices is presented in this article. This model is based on the drift-diffusion equations which include charge injection, transport, space charge effects, trapping, heterojunction interface and recombination process. The device structure in the simulation is ITO/CuPc （20 nm）/NPD （40 nm）/Alq3 （60 nm）/LiF/Al. There are two heterojunctions which should be dealt with in the simulation. The I-V characteristics, carrier distribution and recombination rate of a device are calculated. The simulation results and measured data are in good agreement.
基金This was work supported in part by the National Nature Science Foundation oChina under Grant No. 60425101.
文摘High performance organic light-emitting devices （OLEDs） have been investigated by using fluorescent bis （2-methyl-8-quinolinolato）（para-phenylphenolato）aluminum（BAlq） as an emissive layer on the performance of multicolor devices consisting of N, N＇-bis-（1-naphthyl）-N,N＇diphenyl- 1,1＇-biphenyl-4,4＇- diamine （NPB） as hole transport layer. The results show that the performance of heterostructure blue light-emitting device composed of 8-hydroxyquinoline aluminum （Alq3） as an electron transport layer has been dramatically enhanced. In the case of high performance heterostructure devices, the electroluminescent spectra has been perceived to vary strongly with the thickness of the organic layers due to the different recombination region, which indicates that various color devices composed of identical components could be implemented by changing the film thickness of different functional layers.
基金supported by the National Natural Science Foundation of China(Grant No.60906022)the Natural Science Foundation of Tianjin,China(Grant No.10JCYBJC01100)+2 种基金the Scientific Developing Foundation of Tianjin Education Commission,China(Grant No.2011ZD02)the Key Science and Technology Support Program of Tianjin,China(Grant No.14ZCZDGX00006)the National High Technology Research and Development Program of China(Grant No.2013AA014201)
文摘We investigate the electron injection effect of inserting a thin aluminum（Al） layer into cesium carbonate（Cs2CO3）injection layer. Two groups of organic light-emitting devices（OLEDs） are fabricated. For the first group of devices based on Alq3, we insert a thin Al layer of different thickness into Cs2CO3 injection layer, and the device＇s maximum current efficiency of 6.5 cd/A is obtained when the thickness of the thin Al layer is 0.4 nm. However, when the thickness of Al layer is 0.8 nm, the capacity of electron injection is the strongest. To validate the universality of this approach, then we fabricate another group of devices based on another blue emitting material. The maximum current efficiency of the device without and with a thin Al layer is 4.51 cd/A and 4.84 cd/A, respectively. Inserting a thin Al layer of an appropriate thickness into Cs2CO3 layer can result in the reduction of electron injection barrier, enhancement of the electron injection, and improvement of the performance of OLEDs. This can be attributed to the mechanism that thermally evaporated Cs2CO3 decomposes into cesium oxides, the thin Al layer reacts with cesium oxides to form Al–O–Cs complex, and the amount of the Al–O–Cs complex can be controlled by adjusting the thickness of the thin Al layer.
基金Excellent Youth Foundation of Hunan Province(03JJY1008) Science Foundation for Post-doctorate of China(2004035083)
文摘A bilayer model with ohmic anode contact and injection limited cathode contact has been proposed to calculate the recombination efficiency and recombination zone width of the device. The effects of the thickness of hole transport layer and the barriers of organic/organic interface on the combination efficiency and recombination width have been discussed. It is found that： （1） When the electrons are blocked fully and the holes are not blocked significantly at the organic/organic interface, for a given Lh/L, the recombination efficiency increases with increasing the applied voltage, but at a higher applied voltage, the recombination efficiency decreases with increasing Lh/L; （2） The recombination efficiency increases with increasing applied voltage and Hh＇, and when applied voltage and Hh＇ exceed some value, the recombination efficiency appears as a plateau; （3） The recombination width decreases with increasing the applied voltage and Lh/L. This model might explain the relative experiment phenomena.
基金supported by the National Natural Science Foundation of China(Grant Nos.61905086,62174067,62175085)Science and Technology Development Planning of Jilin Province(Project Nos.20190101024JH,20200201296JC)+1 种基金the Hong Kong Scholars Program(Project No.XJ2020028)grants from the Research Grants Council of the Hong Kong Special Administrative Region,China(Project Nos.11300418 and 11300419).
文摘Here,this work presents an air-stable ultrabright inverted organic lightemitting device(OLED)by using zinc ionchelated polyethylenimine(PEI)as electron injection layer.The zinc chelation is demonstrated to increase the conductivity of the PEI by three orders of magnitude and passivate the polar amine groups.With these physicochemical properties,the inverted OLED shows a record-high external quantum efficiency of 10.0% at a high brightness of 45,610 cd m^(-2) and can deliver a maximum brightness of 121,865 cd m^(-2).Besides,the inverted OLED is also demonstrated to possess an excellent air stability(humidity,35%)with a half-brightness operating time of 541 h@1000 cd m^(-2) without any protection nor encapsulation.
基金Supported by the National Natural Science Foundation of China(No. 20372060), the Key National Natural Science Foundationof China(No. 20131010), the Important National Natural Science Foundation of China(No. 20490210), the"863"Program(Nos.2002AA302105 and 2002AA324080) and Foreign Communion &Cooperation of National Natural Science Foundation of China(No.20340420326).
文摘The dependence of the performance of organic light-emitting devices（OLEDs） on the sheet resistance of indiumtin-oxide（ITO） anodes was investigated by measuring the steady state current density brightness voltage characteristics and the electroluminescent spectra. The device with a higher sheet resistance anode shows a lower current density, a lower brightness level, and a higher operation voltage. The electroluminescence（EL） efficiencies of the devices with the same structure but different ITO anodes show more complicated differences. Furthermore, the shift of the light-emitting zone toward the anode was found when an anode with a higher sheet resistance was used. These performance differences are discussed and attributed to the reduction of hole injection and the increase in voltage drop over ITO anode with the increase in sheet resistance.
基金supported by the Natural Science Foundation of the Shanghai Committee of Science and Technology,China (GrantNo. 08JC1402300)
文摘This paper reports that the doped bi-layer organic light-emitting devices are fabricated by doping in different regions of the light-emitting layer, the admittance and luminance spectra to characterize the capacitance and luminance of the device are measured. Negative capacitance （NC） appeared at low frequencies when the doped devices are biased with high voltages. The measured phase difference between AC voltage applied across the device and AC current flowing through the device show that the device is inductive when NC appears.
基金Project supported by the State Key Development Program for Basic Research of China (Grant No. 2009CB930600)the National Natural Science Foundation of China (Grant Nos. 60907047,61274065,60977024,21101095,20974046,21003076,51173081,and 61136003)+3 种基金the Specialized Research Foundation for the Doctoral Program of Higher Education,China (Grant No. 20093223120003)the Natural Science Foundation of Institutions of Higher Education of Jiangsu Province,China (Grant Nos. SJ209003,09KJB150009,10KJB510013,and TJ209035)the "Qing Lan" Program of Jiangsu Province,Chinathe Program of Nanjing University of Posts and Telecommunications,China (Grant Nos. NY210015,NY211069,and NY210040)
文摘In this paper we report on a high-contrast top-emitting organic light-emitting device utilizing a moderate-reflection contrast-enhancement stack and a high refractive index anti-reflection layer.The contrast-enhancement stack consists of a thin metal anode layer,a dielectric bilayer,and a thick metal underlayer.The resulting device,with the optimized contrast-enhancement stack thicknesses of Ni（30 nm）/MgF 2（62 nm）/ZnS（16 nm）/Ni（20 nm） and the 25-nm-thick ZnS anti-reflection layer,achieves a luminous reflectance of 4.01% in the visible region and a maximum current efficiency of 0.99 cd/A（at 62.3 mA/cm 2） together with a very stable chromaticity.The contrast ratio reaches 561：1 at an on-state brightness of 1000 cd/m^2 under an ambient illumination of 140 lx.In addition,the anti-reflection layer can also enhance the transmissivity of the cathode and improve light out-coupling by the effective restraint of microcavity effects.
基金Natural Science Research Item of Education Department of Henan Province(2008A430009)Doctor Foundation of Henan Polytechnic University(B2008-22)
文摘A new structure containing negative refractive index dielectric layer（NRlDL） is introduced into microcavity. The properties of the new mierocavity organic light-emitting devices（MOLEDs） are investigated. In the experiment, the transfer matrix method is adopted. The dependence of reflectance and transmittance on the refractive index and thickness of NRIDL are analyzed in detail. Compared with the electroluminescence spectra of non-NRIDL diodes, the line widths of the spectra of the MOLEDs are narrower and all the peaks enhance. The results show that the new structure is beneficial to improve the performance and reduce the thickness of microcavity devices.
基金supported by National Science Foun-dation of China (Grant No. 60425101)Program for New CenturyExcellent Talents in University of Education Ministry of China(Grant No. NCET-06-0812)the Young Excellence Project ofUESTC (Grant No.060206.)
文摘A triple layer organic light-emitting diode (OLED) with two heterostructure of indium-tin oxide (ITO)/N,N’-diphenyl-N, N’-bis(1-naphthyl) (1,1’-biphenyl)-4,4’-diamine (NPB)/2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP)/ 8-Hydrox- yquinoline aluminum (Alq3)/Mg:Ag has been fabricated by using the vacuum deposition method. The influence of different film thickness of BCP layer on the performance of the OLEDs has been investigated. The results show that when the thickness of the BCP layer film gradually r...
基金Project supported by the National Natural Science Foundation of China(Grant No.60906022)the Natural Science Foundation of Tianjin,China(Grant No.10JCYBJC01100)+1 种基金the Key Science and Technology Support Program of Tianjin,China(Grant No.14ZCZDGX00006)the National High Technology Research and Development Program of China(Grant No.2013AA014201)
文摘We chose pentacene as a hole injection layer（HIL） to fabricate the high performance blue fluorescent organic lightemitting devices（OLEDs）. We found that the carrier mobility of the pentacene thin films could be efficiently improved after a critical annealing at temperature 120℃. Then we performed the tests of scanning electron microscopy, atomic force microscopy, and Kelvin probe to explore the effect of annealing on the pentacene films. The pentacene film exhibited a more crystalline form with better continuities and smoothness after annealing. The optimal device with 120℃ annealed pentacene film and n-doped electron transport layer（ETL） presents a low turn-on voltage of 2.6 V and a highest luminance of 134800 cd/m^2 at 12 V, which are reduced by 26% and improved by 50% compared with those of the control device.
基金supported by the National Natural Science Foundation of China(No.51973020)Beijing Natural Science Foundation(No.2232052)。
文摘A binary-mixed electron transport layer(ETL)has been reported for constructing solution-processable near-infrared organic light-emitting diodes(NIR OLEDs).Relative to the single-component ETL,the binarymixed ETL composed of PDINN:TPBi can enhance the carrier transport capacity,reduce device impedance,and weaken fiuorescence quenching of the emitting layer.By carefully selecting an appropriate luminescent material Y5(a nonfullerene electron acceptor in organic solar cells)and precisely fine-tuning the molecular aggregation in active layer using a mixed solvent,the morphology is optimized and luminescence performance is enhanced,resulting in efficient NIR OLEDs with an emission peak at 890 nm.The experiment showcases a Y5-based near-infrared OLED with a maximum radiance of 34.9 W sr^(-1)m^(-2)and a maximum external quantum efficiency of 0.50%,which is among the highest values reported for nondoped fiuorescent NIR OLEDs with an emission peak over 850 nm.
基金supported by the National Natural Science Foundation of China (Nos. 62222503, 52073040 and 52130304)the Sichuan Science and Technology Program (Nos. 2024NSFSC0012,2023NSFSC1973 and 2024NSFSC1446)+2 种基金the China Postdoctoral Science Foundation (Nos. 2023M740504 and GZC20230380)the Sichuan Provincial Human Resources and Social Security Department Programthe Collaborative Innovation Center of Suzhou Nano Science&Technology
文摘Triphenylamine(TPA)is the most promising donor fragment for the construction of long-wavelength thermally activated delayed fluorescence(TADF)emitters owing to its suitable dihedral angle that could enhance radiative decay to compete with the serious non-radiative decay.However,the moderate electron-donating capacity of TPA seriously limits the selection of acceptor for constructing longwavelength TADF emitters with narrow bandgaps.To address this issue,in this work,the peripheral benzene of TPA was replaced with 1,4-benzodioxane and anisole to obtain two new electrondonating units N-(2,3-dihydrobenzo[b][1,4]dioxin-6-yl)-N-phenyl-2,3-dihydrobenzo[b][1,4]dioxin-6-amine(TPADBO,−5.02 eV)and 4-methoxy-N-(4-methoxyphenyl)-N-phenylaniline(TPAMO,−5.00 eV),which possess much shallower highest occupied molecule orbital(HOMO)energy levels than the prototype TPA(−5.33 eV).Based on TPA and the modified TPA donor fragments,three TADF emitters were designed and synthesized,namely Py-TPA,Py-TPADBO and Py-TPAMO,with the same acceptor fragment 12-(2,6-diisopropylphenyl)pyrido[2′,3′:5,6]pyrazino[2,3-f][1,10]phenanthroline(Py).Among them,Py-TPAMO exhibits the highest photoluminescence quantum yield of 78.4%and the smallest singlet-triplet energy gap,which is because the introduction of anisole does not cause significant molecule deformation for the excited Py-TPAMO.And Py-TPAMO-based OLEDs successfully realize a maximum external quantum efficiency of 25.5%with the emission peak at 605 nm.This work provides a series of candidate of donor fragments for the development of efficient long-wavelength TADF emitters.
基金financial support of National Key Research and Development Program of China(No.2021YFA1501500)the National Natural Science Foundation of China(Nos.22033008,22220102005,22171265)Fujian Science&Technology Innovation Laboratory for Optoelectronic Information of China(No.2021ZZ103).
文摘The growing environmental concerns regarding rare earth elements in fluorescent powders,along with high production costs,have increased the demand for sustainable alternatives.We propose a promising solution using luminescent metal-organic frameworks(LMOFs)with large surface areas and tunable pore structures,combined with organic carbon quantum dots(CQDs).This study develops a novel white lightemitting diode(WLED)fluorescent powder by incorporating yellow-fluorescent quantum dots(CQDs-Y)into blue-emitting LMOF(ZJU-28),forming the composite material CQDs-Y-n@ZJU-28.The composite exhibits excellent thermal and chemical stability,long-term storage performance,and emits warm white light(CIE:0.3277,0.3281)when subjected to excitation at 365 nm,along with an external quantum efficiency(EQE)of 8.85%.Furthermore,it exhibits tunable emission characteristics and promising LED performance,showcasing a color rendering index(CRI)of 78 and a correlated color temperature of 3384 K.The emitted light undergoes minimal deviation in color towards the white end of the spectrum in the temperature range of 277-437 K,making it an ideal candidate for advanced WLED applications.
基金supported by the National Natural Science Foundation of China(51373190)
文摘A novel bipolar host tris(4-(pyrimidin-5-yl)phenyl)amine(TPMTPA) constructed by incorporating triphenylamine as the electron-donating core and pyrimidine as the electron-accepting peripheries was designed and synthesized.TPMTPA achieves excellent bipolar charge transport properties and has high enough triplet energy level to sensitize green,yellow,orange,red and deep-red phosphors.By using TPMTPA as a host,high performance green,yellow,orange,red and deep-red phosphorescent organic light-emitting devices(PhOLEDs) were demonstrated with maximum external quantum efficiencies of 20.4%,17.6%,15.1%,15.3%and 15.7%respectively.These results suggested that TPMTPA is a versatile high performance host for PhOLEDs of different emission colors.
基金Supported by the National Natural Science Foundation of China (Grant No. 60806047)Research Programs for Science and Technology of Chongqing Municipal Education Commission (Grant No. KJ080816)Natural Science Foundation of Chongqing Normal University (Grant No. 07XLB015)
文摘Highly efficient stacked organic light-emitting devices (OLEDs) have been fabricated using Mg:Alq3:BCP/ WO3 as a novel intermediate layer, which connects two identical emissive units. The stacked OLEDs consisting of NPB/Alq3 exhibited high current efficiency and brightness characteristics over conven- tional single-unit device. At 200 mA/cm2, the current efficiency of the stacked OLEDs using the inter- mediate layers of Mg:Alq3:BCP/WO3 were about 6.85 cd/A, doubling that of the conventional device. The results may prove the method to be effective to enhance the current efficiency and brightness of OLEDs.
基金supported by the Fundamental Research Funds for the Central Universities(08143034)the National Basic Research Program of China(2013CB328705)the National Natural Science Foundation of China(61275034,61106123)
文摘In this article, we reported the synthesis and characterization of a novel silafluorene-based host material, 1,3-bis（5-methyl-5H- dibenzo[b,d]silol-5-yl）benzene （Me-DBSiB）, for blue phosphorescent organic light-emitting devices （PHOLEDs）. The Me- DBSiB was constructed by linking 9-methyl-9-silafluorene units to the phenyl framework through the sp3-hybridized silica atom to maintain high singlet and triplet energy, as well as to enhance thermal and photo-stability. The calculated result shows that the phenyl core does not contribute to both the highest occupied molecular orbital and lowest unoccupied molecular orbital. Wide optical energy gap of 4.1 eV was achieved. When the Me-DBSiB was used as the host and iridium （Ⅲ） bis[（4,6-difluorophenyl）pyridinato-N,C2＇]picolate （Firpic） as the vip, a maximum current efficiency was 14.8 cd/A, lower than the counterpart of 1,3-bis（9-carbazolyl）benzene （28 cd/A）. The unbalanced barrier for electron and hole injection to host layer may be responsible for low efficiency. Even so, our results show that silafluorene moieties are promising building blocks for constructing wide-energy-gap host materials.
