Remarkable progress was made in the development of white-light-emitting diodes （LEDs）. White LEDs provided a light element having a semiconductor InGaN light-emitting chip （blue or UV LEDs） and luminescent phospho...Remarkable progress was made in the development of white-light-emitting diodes （LEDs）. White LEDs provided a light element having a semiconductor InGaN light-emitting chip （blue or UV LEDs） and luminescent phosphors. Here we reported the sialon s-phase of （Sr,Eu）2A12Si10N14O4. Eu^2＋ activator ions that were substituted for the strontium site represented a new type of yeUow-green phosphor that could be excited by blue LEDs used for application in the fabrication of white LEDs.展开更多
White organic light-emitting diodes （WOLEDs） with a structure of indium-tin-oxide （ITO）/N,N＇-bis- （1-naphthyl）-N,N＇-diphenyl- （1, 1＇-biphenyl）-4,4＇-diamine （NPB）/1,2,3,4,5,6-hexakis（9,9-diethyl-9H-fluor...White organic light-emitting diodes （WOLEDs） with a structure of indium-tin-oxide （ITO）/N,N＇-bis- （1-naphthyl）-N,N＇-diphenyl- （1, 1＇-biphenyl）-4,4＇-diamine （NPB）/1,2,3,4,5,6-hexakis（9,9-diethyl-9H-fluoren-2- yl）benzene （HKEthFLYPh）/5,6,11,12-tetraphenylnaphtacene （rubrene）/tris（8-hydroxyquinoline） aluminum （Alq3）/Mg：Ag were fabricated by vacuum deposition method, in which a novel star-shaped hexafluorenyl- benzene HKEthFLYPh was used as an energy transfer layer, and an ultrathin layer of rubrene was inserted between HKEthFLYPh and Alq3 layers as a yellow light-emitting layer instead of using a time-consuming doping process. A fairly pure WOLED with Commissions Internationale De L＇Eclairage （CIE） coordinates of （0.32, 0.33） was obtained when the thickness of rubrene was 0.3 nm, and the spectrum was insensitive to the applied voltage. The device yielded a maximum luminance of 4816 cd/m2 at 18 V.展开更多
Multidimensional influences of indium composition in barrier layers on GaN-based blue laser diodes(LDs)are discussed from both material quality and device physics perspectives.LDs with higher indium content in the bar...Multidimensional influences of indium composition in barrier layers on GaN-based blue laser diodes(LDs)are discussed from both material quality and device physics perspectives.LDs with higher indium content in the barriers demonstrate a notably lower threshold current and shorter lasing wavelength compared to those with lower indium content.Our experiments reveal that higher indium content in the barrier layers can partially reduce indium composition in the quantum wells,a novel discovery.Employing higher indium content barrier layers leads to improved luminescence properties of the MQW region.Detailed analysis reveals that this improvement can be attributed to better homogeneity in the indium composition of the well layers along the epitaxy direction.InGaN barrier layers suppress the lattice mismatch between barrier and well layers,thus mitigating the indium content pulling effect in the well layers.In supplement to experimental analysis,theoretical computations are performed,showing that InGaN barrier structures can effectively enhance carrier recombination efficiency and optical confinement of LD structure,thus improving the output efficiency of GaN-based blue LDs.Combining these theoretical insights with our experimental data,we propose that higher indium content barriers effectively enhance carrier recombination efficiency and indium content homogeneity in quantum well layers,thereby improving the output performance of GaN-based blue LDs.展开更多
Quantum dot light-emitting diodes(QLEDs)have become an important research direction in the pursuit of next-generation display technology owing to their favorable attributes,including high energy efficiency,wide color ...Quantum dot light-emitting diodes(QLEDs)have become an important research direction in the pursuit of next-generation display technology owing to their favorable attributes,including high energy efficiency,wide color gamut,and low cost.Breakthroughs in the luminous efficiency and operating life of QLEDs have been achieved by enhancing the photoluminescence efficiency of the quantum dots(QDs)and optimizing the device structure.However,the current mainstream QDs contain heavy metal elements such as lead and cadmium,which restrict the development and application of QD displays.Exploring new types of environmentally friendly QDs is crucial.I-III-VI semiconductor QDs have been developed as luminescent materials for constructing high color rendering index QLEDs,owing to the outstanding photophysical properties of these QDs,such as composition-dependent tunable bandgap,large Stokes shift,and highefficiency luminescence.Currently,the microstructures of heterojunctions,especially the surface states and interface states,affect the recombination and transport of carriers in electroluminescent(EL)devices with multilayer thin film structures,which in turn influence the luminous efficiency and stability of the device.This review focuses on the synthesis strategies of I-III-VI multi-component QDs and provides an in-depth understanding of the luminescence mechanism and the regulation of photophysical and electronic properties.Furthermore,the application of I-III-VI QDs in multi-color and white EL QLEDs is discussed and the challenges and outlook are addressed.展开更多
Thermally activated delayed fluorescence(TADF)organic light-emitting diodes(OLEDs)have been demonstrated in applications such as displays and solid-state lightings.However,weak stability and ineffi-cient emission of b...Thermally activated delayed fluorescence(TADF)organic light-emitting diodes(OLEDs)have been demonstrated in applications such as displays and solid-state lightings.However,weak stability and ineffi-cient emission of blue TADF OLEDs are two key bottlenecks limiting the development of solution processable displays and white light sources.This work presents a solution-processed OLED using a blue-emitting TADF small molecule bis[4-(9,9-dimethyl-9,10-dihydroacridine)phenyl]sulfone(DMAC-DPS)as an emitter.We comparatively investigated the effects of single host poly(Nvinylcarbazole)(PVK)and a co-host of 60%PVK and 30%2,2′-(1,3-phenylene)-bis[5-(4-tert-butylphenyl)-1,3,4-oxadiazole](OXD-7)on the device performance(the last 10%is emitter DMAC-DPS).The co-host device shows lower turn-on voltage,similar maximum luminance,and much slower external quantum efficiency(EQE)rolloff.In other words,device stability improved by doping OXD-7 into PVK,and the device impedance simultaneously and significantly reduced from 8.6103 to 4.2103 W at 1000 Hz.Finally,the electroluminescent stability of the co-host device was significantly enhanced by adjusting the annealing temperature.展开更多
To increase the current density of the hole only device, 1, 4, 5, 8, 9, 11-hexaazatriphenylene-hexacarbonitrile (HAT-CN) material has been inserted in the device at the indium tin oxide (ITO)/organic interface. Since ...To increase the current density of the hole only device, 1, 4, 5, 8, 9, 11-hexaazatriphenylene-hexacarbonitrile (HAT-CN) material has been inserted in the device at the indium tin oxide (ITO)/organic interface. Since HATCN molecule can withdraw electrons, it can alter electronic properties of the electrodes and hence inserted between the organic/metal interfaces. This paper deals with the optimization of the thickness of organic-metal layers to enhance the efficiency. Also, efforts have been made to increase the current density and reduce the operating voltage of the device. The material 2, 7-bis [N, N-bis (4- methoxy-phenyl) amino]-9, 9-spirobifluorene (Meo-Spiro-TPD) is used to simulate the hole only device because it is a thermally stable hole transport material. Simulated results shows that better current density values can be achieved compared to fabricated one by optimizing the organic metal layer thickness. The best optimized layer thickness of 22 nm for Alq3, 25 nm for *CBP doped with Ir(ppy)3, 9 nm for Meo-Spiro TPD and 4 nm for HAT-CN which results in current density of 0.12 A/cm2 with a reduction in operating voltage by approximately 2 V.展开更多
基金Project supported by the Economic Affair (95-EC-17-A-07-S1-043)the National Science Council (94-2113-M-002-030)
文摘Remarkable progress was made in the development of white-light-emitting diodes （LEDs）. White LEDs provided a light element having a semiconductor InGaN light-emitting chip （blue or UV LEDs） and luminescent phosphors. Here we reported the sialon s-phase of （Sr,Eu）2A12Si10N14O4. Eu^2＋ activator ions that were substituted for the strontium site represented a new type of yeUow-green phosphor that could be excited by blue LEDs used for application in the fabrication of white LEDs.
基金This work was supported by the National Natural Science Foundation of China （No.60425101 and No.20674049）, the Program for New Century Excellent Talents in University （No.NCET-06-0812）, and the Young Talent Project at University of Electronic Science and Technology of China （No.060206）.
文摘White organic light-emitting diodes （WOLEDs） with a structure of indium-tin-oxide （ITO）/N,N＇-bis- （1-naphthyl）-N,N＇-diphenyl- （1, 1＇-biphenyl）-4,4＇-diamine （NPB）/1,2,3,4,5,6-hexakis（9,9-diethyl-9H-fluoren-2- yl）benzene （HKEthFLYPh）/5,6,11,12-tetraphenylnaphtacene （rubrene）/tris（8-hydroxyquinoline） aluminum （Alq3）/Mg：Ag were fabricated by vacuum deposition method, in which a novel star-shaped hexafluorenyl- benzene HKEthFLYPh was used as an energy transfer layer, and an ultrathin layer of rubrene was inserted between HKEthFLYPh and Alq3 layers as a yellow light-emitting layer instead of using a time-consuming doping process. A fairly pure WOLED with Commissions Internationale De L＇Eclairage （CIE） coordinates of （0.32, 0.33） was obtained when the thickness of rubrene was 0.3 nm, and the spectrum was insensitive to the applied voltage. The device yielded a maximum luminance of 4816 cd/m2 at 18 V.
基金Project supported by Youth Innovation Promotion Association of the Chinese Academy of Sciences(Grant No.2023124)the National Key Research and Development Program of China(Grant No.2022YFB3608100)+3 种基金Key Research and Development Program of Jiangsu Province(Grant No.BE2021008-1)Shanxi-Zheda Institute of Advanced Materials and Chemical Engineering(Grant No.2022SXTD016)the National Natural Science Foundation of China(Grant Nos.62274157,61904172,62127807,62234011,61974162,62034008,62074142,62074140,and 62250038)Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB43030101)。
文摘Multidimensional influences of indium composition in barrier layers on GaN-based blue laser diodes(LDs)are discussed from both material quality and device physics perspectives.LDs with higher indium content in the barriers demonstrate a notably lower threshold current and shorter lasing wavelength compared to those with lower indium content.Our experiments reveal that higher indium content in the barrier layers can partially reduce indium composition in the quantum wells,a novel discovery.Employing higher indium content barrier layers leads to improved luminescence properties of the MQW region.Detailed analysis reveals that this improvement can be attributed to better homogeneity in the indium composition of the well layers along the epitaxy direction.InGaN barrier layers suppress the lattice mismatch between barrier and well layers,thus mitigating the indium content pulling effect in the well layers.In supplement to experimental analysis,theoretical computations are performed,showing that InGaN barrier structures can effectively enhance carrier recombination efficiency and optical confinement of LD structure,thus improving the output efficiency of GaN-based blue LDs.Combining these theoretical insights with our experimental data,we propose that higher indium content barriers effectively enhance carrier recombination efficiency and indium content homogeneity in quantum well layers,thereby improving the output performance of GaN-based blue LDs.
基金financially supported by the Science and Technology Project of Hebei Education Department(QN2021122)the Natural Science Foundation of Hebei Province(F2022408002)+1 种基金the Science Research Start-up Funding of Langfang Normal University(XBQ202305)the National Natural Science Foundation of China(51902054)。
文摘Quantum dot light-emitting diodes(QLEDs)have become an important research direction in the pursuit of next-generation display technology owing to their favorable attributes,including high energy efficiency,wide color gamut,and low cost.Breakthroughs in the luminous efficiency and operating life of QLEDs have been achieved by enhancing the photoluminescence efficiency of the quantum dots(QDs)and optimizing the device structure.However,the current mainstream QDs contain heavy metal elements such as lead and cadmium,which restrict the development and application of QD displays.Exploring new types of environmentally friendly QDs is crucial.I-III-VI semiconductor QDs have been developed as luminescent materials for constructing high color rendering index QLEDs,owing to the outstanding photophysical properties of these QDs,such as composition-dependent tunable bandgap,large Stokes shift,and highefficiency luminescence.Currently,the microstructures of heterojunctions,especially the surface states and interface states,affect the recombination and transport of carriers in electroluminescent(EL)devices with multilayer thin film structures,which in turn influence the luminous efficiency and stability of the device.This review focuses on the synthesis strategies of I-III-VI multi-component QDs and provides an in-depth understanding of the luminescence mechanism and the regulation of photophysical and electronic properties.Furthermore,the application of I-III-VI QDs in multi-color and white EL QLEDs is discussed and the challenges and outlook are addressed.
基金the National Key Research and Development Program of China(No.2017YFB0404404)the Open Fund of State Key Laboratory of Luminescent Materials and Devices(South China University of Technology),China。
文摘Thermally activated delayed fluorescence(TADF)organic light-emitting diodes(OLEDs)have been demonstrated in applications such as displays and solid-state lightings.However,weak stability and ineffi-cient emission of blue TADF OLEDs are two key bottlenecks limiting the development of solution processable displays and white light sources.This work presents a solution-processed OLED using a blue-emitting TADF small molecule bis[4-(9,9-dimethyl-9,10-dihydroacridine)phenyl]sulfone(DMAC-DPS)as an emitter.We comparatively investigated the effects of single host poly(Nvinylcarbazole)(PVK)and a co-host of 60%PVK and 30%2,2′-(1,3-phenylene)-bis[5-(4-tert-butylphenyl)-1,3,4-oxadiazole](OXD-7)on the device performance(the last 10%is emitter DMAC-DPS).The co-host device shows lower turn-on voltage,similar maximum luminance,and much slower external quantum efficiency(EQE)rolloff.In other words,device stability improved by doping OXD-7 into PVK,and the device impedance simultaneously and significantly reduced from 8.6103 to 4.2103 W at 1000 Hz.Finally,the electroluminescent stability of the co-host device was significantly enhanced by adjusting the annealing temperature.
文摘To increase the current density of the hole only device, 1, 4, 5, 8, 9, 11-hexaazatriphenylene-hexacarbonitrile (HAT-CN) material has been inserted in the device at the indium tin oxide (ITO)/organic interface. Since HATCN molecule can withdraw electrons, it can alter electronic properties of the electrodes and hence inserted between the organic/metal interfaces. This paper deals with the optimization of the thickness of organic-metal layers to enhance the efficiency. Also, efforts have been made to increase the current density and reduce the operating voltage of the device. The material 2, 7-bis [N, N-bis (4- methoxy-phenyl) amino]-9, 9-spirobifluorene (Meo-Spiro-TPD) is used to simulate the hole only device because it is a thermally stable hole transport material. Simulated results shows that better current density values can be achieved compared to fabricated one by optimizing the organic metal layer thickness. The best optimized layer thickness of 22 nm for Alq3, 25 nm for *CBP doped with Ir(ppy)3, 9 nm for Meo-Spiro TPD and 4 nm for HAT-CN which results in current density of 0.12 A/cm2 with a reduction in operating voltage by approximately 2 V.
