The effect of a benzimidazole derivative(TPBI)electron injection layer(EIL)on the performance of Alga based organic light-emitting devices(OLEDs)with a Cs_(2)C0_(3)/Al cathode is investigated.An increasing current den...The effect of a benzimidazole derivative(TPBI)electron injection layer(EIL)on the performance of Alga based organic light-emitting devices(OLEDs)with a Cs_(2)C0_(3)/Al cathode is investigated.An increasing current density from 71.9mA/cm2 to 188.3mA/cm^(2),and an enhanced electroluminescence(EL)efficiency from 3.2cd/A to 3.64 cd/A at 9 V are found when a thin TPBI layer(5 nm)is inserted at the Alq_(3)/Cs_(2)C0_(3)interface.After further increasing the TPBI thickness to 10 run,OLEDs display a further increase in EL efficiency to 4.53cd/A.Our experiment suggests that the TPBI thin layer at the Alq_(3)/Cs_(2)C0_(3)interface facilitates the electron injection and is also involved with hole-blocking and exciton confinement.展开更多
A simple method to determine the traps＇ density of state （DOS） in organic light-emitting diodes （OLEDs） by manipulating the current-voltage （I-V） characteristic of the devices at room temperature is introduced....A simple method to determine the traps＇ density of state （DOS） in organic light-emitting diodes （OLEDs） by manipulating the current-voltage （I-V） characteristic of the devices at room temperature is introduced. In particular, the trap-dependent space-charge limited current formula is simplified to obtain effective density of traps. In this study, poly[（9,9-di-n-octylfluorenyl-2,7-diyl）-alt-（benzo[2,1,3]thiadiazol-4,8-diyl）] （F8BT） and 2- Methoxy-5-（3＇, 7＇-dimethyloctyloxy） benzene-l,4-diacetonitrile （0C1 Clo-PPV） are selected as the OLEDs emissive layer. The trap DOS of F8BT- and OC1Clo-PPV-based OLEDs are calculated in the magnitudes of 1024 m^-3 and 1023 m^-3, respectively. In addition, the results agree with the other conventional method which is used to determine the trap DOS in OLEDs. This calculation technique may serve as a robust and reliable approach to obtain the trap DOS in OLEDs at room temperature.展开更多
The calculation of the external quantum efficiency(η_ ext ) of organic light-emitting devices(OLEDs) is presented theoretically. The basic idea is to obtain η_ ext by calculating the fraction of the generated light ...The calculation of the external quantum efficiency(η_ ext ) of organic light-emitting devices(OLEDs) is presented theoretically. The basic idea is to obtain η_ ext by calculating the fraction of the generated light that can escape through the top surface and the average transmittance over the escape cone. During the calculation, the effects of the interference, absorption and multiple reflections are neglected. Then a result of a typical 8-tris-hydroxyquinoline aluminum(Alq_ 3 )-based OLEDs on a planar glass substrate is obtained. And a twice increase in η_ ext can be achieved by using a high-index-glass substrate with an antireflection coating(SiO_ 2 ) on substrate surface.展开更多
The effect of LiF thickness on the electrical and luminescent characteristics in OLEDs has been studied by carefully varying thickness value range from 0 nm to 1.2 nm. It’s interesting to find that the device with 0....The effect of LiF thickness on the electrical and luminescent characteristics in OLEDs has been studied by carefully varying thickness value range from 0 nm to 1.2 nm. It’s interesting to find that the device with 0.2 nm LiF layer performs the largest current and comparative lower luminescent efficiency, while the one with 0.6 nm LiF performs another current peak (lower than that of device with 0.2 nm LiF layer) but the highest luminescent efficiency in all devices. Here the much enhanced electron injection and destructive efficiency for 0.2 nm LiF device are understood by the chemical interaction model at cathode interface, while the fairly increased electron injection and much improved efficiency for 0.6 nm LiF device would be interpreted by other mechanisms, and LiF plays a protective part in preventing the deposition-induce photoluminescence from quenching by Al cathode.展开更多
We fabricate a series of samples and OLEDs with organic multilayer quantum well structure, which consist of alternate PBD and Alqy Both PBD and Alq3 are electron-transporting materials, and PBD is used as potential ba...We fabricate a series of samples and OLEDs with organic multilayer quantum well structure, which consist of alternate PBD and Alqy Both PBD and Alq3 are electron-transporting materials, and PBD is used as potential barrier layer, while Alq3 is used as potential well layer and emitting layer. Compared with double-layer structure, the luminescent characteristics of organic samples and diodes with quantum well structure are investigated and the quantum well structure helps the energy transfer between well layer and barrier layer. The quantum well structure makes carriers disperse in the different well layers and then increases the number of excitons to enhance the efficiency of the recombination.展开更多
Triphenylamine(TPA)-containing 2-(2-hydroxyphenyl)benzoxazoles(2a-2c)have been synthesized via a highly efficient rhodium-catalyzed C–H/C–H cross-coupling reaction.Compound 2a is a novel mechanofluorochromic materia...Triphenylamine(TPA)-containing 2-(2-hydroxyphenyl)benzoxazoles(2a-2c)have been synthesized via a highly efficient rhodium-catalyzed C–H/C–H cross-coupling reaction.Compound 2a is a novel mechanofluorochromic material with blue-shifted mechanochromic properties.Compounds 2b and 2c presented opposite mechanochromic trends.For 2b,the enol-form emission enhanced,and the ketoform emission blue-shift after grinding.In contrast,2c exhibited the weak enol-form emission disappeared and the keto-form emission slightly red-shift after grinding treatments.The estrone-containing2b-based water-dispersed nanoparticles(NPs)exhibit apparent dual-emission and were applied for fluorescence images.In addition,bis(TPA)-containing 2c-based devices exhibit dual-emission with good performance and a singlet exciton yield of 92%,which breaks through the theoretical upper limit of 25%in conventional fluorescent OLEDs.This is one of the highest exciton utilization values recorded for the ESIPT molecules with a dual emission system.展开更多
The development of high-performance solution-processed red organic light-emitting diodes(OLEDs) remains a challenge,particularly in terms of maintaining efficiency at high luminance. Here, we designed and synthesized ...The development of high-performance solution-processed red organic light-emitting diodes(OLEDs) remains a challenge,particularly in terms of maintaining efficiency at high luminance. Here, we designed and synthesized four novel orange-red thermally activated delayed fluorescence(TADF) dendrimers that are solution-processable: 2GCz BP, 2DPACz BP, 2FBP2GCz and 2FBP2DPACz. We systematically investigated the effect of substitution position and strength of donors on the optoelectronic properties. The reverse intersystem crossing rate constant(kRISC) of the emitters having donors substituted at positions 11and 12 of the dibenzo[a,c]phenazine(BP) is more than 10-times faster than that of compounds substituted having donors substituted at positions 3 and 6. Compound 2DPACz BP, containing stronger donors than 2GCz BP, exhibits a red-shifted emission and smaller singlet-triplet energy splitting, ΔE_(ST), of 0.01 e V. The solution-processed OLED with 10 wt% 2DPACz BP doped in m CP emitted at 640 nm and showed a maximum external quantum efficiency(EQE_(max)) of 7.8%, which was effectively maintained out to a luminance of 1,000 cd m-2. Such a device's performance at relevant display luminance is among the highest for solution-processed red TADF OLEDs. The efficiency of the devices was improved significantly by using 4Cz IPN as an assistant dopant in a hyperfluorescence(HF) configuration, where the 2DPACz BP HF device shows an EQEmaxof 20.0% at λEL of 605 nm and remains high at 11.8% at a luminance of 1,000 cd m-2, which makes this device one of the highest efficiency orange-to-red HF SP-OLEDs to date.展开更多
基金Patent Industrialization Project of Shaanxi Province(No.2005ZZ-04)Industrialization Project of Shaanxi Education Office(No.06JC23)Patent Scientific Research Project of Shaanxi Education Office(No.07JK191)
基金Supported by the National Natural Science Foundation of China under Grant No 20972097Guangdong-Provincial Natural Science Foundation(No 031805)+2 种基金the Major Program in Key Field of Guangdong Province Government(No 2003-03)Science and Technology Program of Shenzhen(No 2006-2007)the Project 000011 Supported by SZU R/D Fund,Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province.
文摘The effect of a benzimidazole derivative(TPBI)electron injection layer(EIL)on the performance of Alga based organic light-emitting devices(OLEDs)with a Cs_(2)C0_(3)/Al cathode is investigated.An increasing current density from 71.9mA/cm2 to 188.3mA/cm^(2),and an enhanced electroluminescence(EL)efficiency from 3.2cd/A to 3.64 cd/A at 9 V are found when a thin TPBI layer(5 nm)is inserted at the Alq_(3)/Cs_(2)C0_(3)interface.After further increasing the TPBI thickness to 10 run,OLEDs display a further increase in EL efficiency to 4.53cd/A.Our experiment suggests that the TPBI thin layer at the Alq_(3)/Cs_(2)C0_(3)interface facilitates the electron injection and is also involved with hole-blocking and exciton confinement.
基金Supported by the Science Fund under Grant No SF019-2013the Fundamental Research Grant Scheme under Grant No FP033-2013B+1 种基金the Postgraduate Research Fund under Grant No PG107-2015Athe University Malaya Research Grant under Grant No RP026B-15AFR
文摘A simple method to determine the traps＇ density of state （DOS） in organic light-emitting diodes （OLEDs） by manipulating the current-voltage （I-V） characteristic of the devices at room temperature is introduced. In particular, the trap-dependent space-charge limited current formula is simplified to obtain effective density of traps. In this study, poly[（9,9-di-n-octylfluorenyl-2,7-diyl）-alt-（benzo[2,1,3]thiadiazol-4,8-diyl）] （F8BT） and 2- Methoxy-5-（3＇, 7＇-dimethyloctyloxy） benzene-l,4-diacetonitrile （0C1 Clo-PPV） are selected as the OLEDs emissive layer. The trap DOS of F8BT- and OC1Clo-PPV-based OLEDs are calculated in the magnitudes of 1024 m^-3 and 1023 m^-3, respectively. In addition, the results agree with the other conventional method which is used to determine the trap DOS in OLEDs. This calculation technique may serve as a robust and reliable approach to obtain the trap DOS in OLEDs at room temperature.
基金National Natural Science Foundation of China(60207003 and 60376028) National"973"Project of China(2003cb314703)
文摘The calculation of the external quantum efficiency(η_ ext ) of organic light-emitting devices(OLEDs) is presented theoretically. The basic idea is to obtain η_ ext by calculating the fraction of the generated light that can escape through the top surface and the average transmittance over the escape cone. During the calculation, the effects of the interference, absorption and multiple reflections are neglected. Then a result of a typical 8-tris-hydroxyquinoline aluminum(Alq_ 3 )-based OLEDs on a planar glass substrate is obtained. And a twice increase in η_ ext can be achieved by using a high-index-glass substrate with an antireflection coating(SiO_ 2 ) on substrate surface.
文摘The effect of LiF thickness on the electrical and luminescent characteristics in OLEDs has been studied by carefully varying thickness value range from 0 nm to 1.2 nm. It’s interesting to find that the device with 0.2 nm LiF layer performs the largest current and comparative lower luminescent efficiency, while the one with 0.6 nm LiF performs another current peak (lower than that of device with 0.2 nm LiF layer) but the highest luminescent efficiency in all devices. Here the much enhanced electron injection and destructive efficiency for 0.2 nm LiF device are understood by the chemical interaction model at cathode interface, while the fairly increased electron injection and much improved efficiency for 0.6 nm LiF device would be interpreted by other mechanisms, and LiF plays a protective part in preventing the deposition-induce photoluminescence from quenching by Al cathode.
基金This work was Supported by "973" National Key Basic ResearchFoundation of China (No. 2003CB314707)National Natural Sci-ence Foundation of China (No. 60576016 ,10374001, and No.10434030).
文摘We fabricate a series of samples and OLEDs with organic multilayer quantum well structure, which consist of alternate PBD and Alqy Both PBD and Alq3 are electron-transporting materials, and PBD is used as potential barrier layer, while Alq3 is used as potential well layer and emitting layer. Compared with double-layer structure, the luminescent characteristics of organic samples and diodes with quantum well structure are investigated and the quantum well structure helps the energy transfer between well layer and barrier layer. The quantum well structure makes carriers disperse in the different well layers and then increases the number of excitons to enhance the efficiency of the recombination.
基金Jiangsu Key Laboratory of Advanced Catalytic Materials and Technology(No.BM2012110)the fundamental research funds for the central universities(No.2023CDJYGRH-YB17)+4 种基金the Venture&Innovation Support Program for Chongqing Overseas Returnees(No.cx2022061)the Natural Science Foundation of Chongqing(No.CSTB2022NSCQ-MSX1123)the Chongqing Talents:Exceptional Young Talents Project(No.cstc2021ycjh-bgzxm0067)Changzhou University,Advanced Catalysis and Green Manufacturing Collaborative Innovation Center(No.ACGM2022–10–10)National Natural Science Foundation of China(Nos.21702019,62174160)for financial support。
文摘Triphenylamine(TPA)-containing 2-(2-hydroxyphenyl)benzoxazoles(2a-2c)have been synthesized via a highly efficient rhodium-catalyzed C–H/C–H cross-coupling reaction.Compound 2a is a novel mechanofluorochromic material with blue-shifted mechanochromic properties.Compounds 2b and 2c presented opposite mechanochromic trends.For 2b,the enol-form emission enhanced,and the ketoform emission blue-shift after grinding.In contrast,2c exhibited the weak enol-form emission disappeared and the keto-form emission slightly red-shift after grinding treatments.The estrone-containing2b-based water-dispersed nanoparticles(NPs)exhibit apparent dual-emission and were applied for fluorescence images.In addition,bis(TPA)-containing 2c-based devices exhibit dual-emission with good performance and a singlet exciton yield of 92%,which breaks through the theoretical upper limit of 25%in conventional fluorescent OLEDs.This is one of the highest exciton utilization values recorded for the ESIPT molecules with a dual emission system.
基金the China Scholarship Council(201806890001)support from the Royal Academy of Engineering Enterprise Fellowship (EF2122-13106)EPSRC (EP/W015137/1, EP/W524505/1) for financial support。
文摘The development of high-performance solution-processed red organic light-emitting diodes(OLEDs) remains a challenge,particularly in terms of maintaining efficiency at high luminance. Here, we designed and synthesized four novel orange-red thermally activated delayed fluorescence(TADF) dendrimers that are solution-processable: 2GCz BP, 2DPACz BP, 2FBP2GCz and 2FBP2DPACz. We systematically investigated the effect of substitution position and strength of donors on the optoelectronic properties. The reverse intersystem crossing rate constant(kRISC) of the emitters having donors substituted at positions 11and 12 of the dibenzo[a,c]phenazine(BP) is more than 10-times faster than that of compounds substituted having donors substituted at positions 3 and 6. Compound 2DPACz BP, containing stronger donors than 2GCz BP, exhibits a red-shifted emission and smaller singlet-triplet energy splitting, ΔE_(ST), of 0.01 e V. The solution-processed OLED with 10 wt% 2DPACz BP doped in m CP emitted at 640 nm and showed a maximum external quantum efficiency(EQE_(max)) of 7.8%, which was effectively maintained out to a luminance of 1,000 cd m-2. Such a device's performance at relevant display luminance is among the highest for solution-processed red TADF OLEDs. The efficiency of the devices was improved significantly by using 4Cz IPN as an assistant dopant in a hyperfluorescence(HF) configuration, where the 2DPACz BP HF device shows an EQEmaxof 20.0% at λEL of 605 nm and remains high at 11.8% at a luminance of 1,000 cd m-2, which makes this device one of the highest efficiency orange-to-red HF SP-OLEDs to date.
