Flexible white top-emitting organic light-emitting diode with a MoO_x roughness improvement layer

In this paper, an MoOx film is deposited on a polyethylene terephthalate （PET） substrate as a buffer layer to improve the surface roughness of the flexible PET substrate. With an optimized MoOx thickness of 100 nm, the surface roughness of the PET substrate can be reduced to a very small value of 0.273 nm （much less than 0.585 nm of the pure PET）. Flexible white top-emitting organic light-emitting diodes （TEOLEDs） with red and blue dual phosphorescent emitting layers are constructed based on a low-reflectivity Sm/Ag semi-transparent cathode. The flexible white emission exhibits the best luminance and current injection characteristics with the 100-nm-thick MoOx buffer layer and this result indicates that a smooth substrate is beneficial to the enhancement of device electrical and electroluminescence performances. However, the white TEOLED with a 50-nm-thick MoOx buffer layer exhibits a maximum current efficiency of 4.64 cd/A and a power efficiency of 1.9 lm/W, slightly higher than those with a 100-nm MoOx buffer layer, which is mainly due to an obvious intensity enhancement but limited current increases in 50-nm MoOx-based white TEOLED. The change amplitudes of the Commission International de l’Eclairage （CIE） chromaticity coordinates are less than （0.016, 0.005） for all devices in a wide luminance range over 100 cd/m2, indicating an excellent color stability in our white flexible TEOLEDs. Additionally, the flexible white TEOLED with an MoOx buffer layer shows excellent flexibility to withstand more than 500 bending times under a curvature radius of approximately 9 mm. Research demonstrates that it is mainly attributed to the high surface energy of the MoOx buffer layer, which is conducible to the improvement of the surface adhesion to the PET substrate and the Ag anode.     

基于ZnS增透膜的顶发射白光有机发光二极管

顶发射白光有机发光二极管(TEWOLED)在白光照明和全彩显示中有着良好的应用前景, 克服顶发射器件中的微腔效应是制备光电性能良好的TEWOLED的前提. 使用具有高折射率的ZnS作为增透膜改善金属阴极在蓝光波段的透射率,降低其反射性, 从而有效抑制了微腔的影响.同时利用转移矩阵理论和宽角干涉方法分别对阴极结构和 蓝光发光层位置进行了优化,最终获得了高效、色纯度良好、色度随视角变化小的TEWOLED. 最高亮度和效率分别达到9213 cd/m²和3 cd/A,色坐标位于白光区且接近白光等能点, 同时具有良好的视角稳定性,在0°---60°范围内色坐标仅变化(0.02, 0).     

Blue organic light-emitting diodes with 2-methyl-9,10-bis(naphthalen-2-yl)anthracene as hole transport and emitting layer and the impedance spectroscopy analysis

2-methyl-9,10-bis(naphthalen-2-yl)anthracene (MADN) based fluorescent blue organic light-emitting diodes (OLEDs) are demonstrated. With MADN as emitting layer, experiments indicate that thick MADN (40–60 nm) is preferable for constructing efficient blue OLED. With MADN as hole-transport and emitting layer and tris(8-hydroxy-quinolinato)aluminium (Alq₃) as electron-transport layer, the OLED electroluminescent characteristics show a mixture emission of MADN and Alq₃ with Commission Internationale d'Eclairage (CIE) color coordinates of (0.25, 0.34), indicating feasible hole transporting in MADN. Using 4,7-diphenyl-1,10-phenanthroline (BPhen) replacing Alq₃ as electron-transport layer, the OLED shows deep blue emission with a maximum luminous efficiency of 4.8 cd/A and CIE color coordinates of (0.16, 0.09). The hole transport characteristics of MADN are further clarified by constructing hole-only device and performing impedance spectroscopy analysis. The results indicate that MADN shows superior hole-transport ability which is almost comparable to typical hole-transport material of N,N′-bis(naphthalen-1-yl)-N,N′-bis(phenyl)-benzidine (NPB), suggesting a promising application for constructing efficient blue OLED with integrated hole-transport layer and emitting layer.     

All-in-one-type organic light-emitting diodes for color tuning using phosphor in glasses with Pb-free silicate powders

We demonstrate all-in-one-type organic light-emitting diodes (OLEDs) that are fabricated using a color converting plate as a substrate. The color converting plate is Pb-free phosphor-in-glass (PiG), which is prepared by mixing Y₃Al₅O₁₂:Ce³⁺ (YAG:Ce³⁺) and SiO₂–B₂O₃–RO (R = Ba, Zn) glass frit by sintering at 750 °C for 30 min. The maximum luminance, luminance efficiency, and power efficiency of blue OLEDs fabricated on commercial glass are measured as 10500 cd/m², 10.18 cd/A, and 2.95 lm/W, respectively. The Commission Internationale de l'Eclairge (CIE) coordinates of blue OLEDs is (0.167, 0.325). Our obtained results show that the luminance value decreased as the PiG thickness increased, and the glass to phosphor (GTP) ratio decreased. The OLED devices fabricated on the PiG substrate (GTP ratio = 9:1, thickness: 150 μm) showed a maximum luminance, luminance efficiency, and power efficiency of 7600 cd/m², 8.76 cd/A, and 2.85 lm/W, respectively. The CIE color coordinates changed to (0.286, 0.504) at 200 mA/cm². These results proved that color coordination can be easily adjusted by varying the GTP ratio and the thickness of the PiG.     

Simple-structure white organic light emitting diodes with high color temperature

We present high color temperature white organic light emitting diodes with a simple p-i-n structure. A sky blue phosphorescent dopant of iridium(III) bis[4,6-(difluorophenyl)-pyridinato-N,C^2’] picolinate and a red phosphorescent dopant of bis(2-phenylquinoline)(acetylacetonate)iridium(III) in the emissive layers is employed to make high color temperature devices. Very stable color variation under ?0.02 until a 5000 cd/m² brightness value is realized by efficient carrier control in a multi stacked emitting layer of blue/red/blue colors. Maximum current and power efficiencies of 23.8 cd/A and 22.9 lm/W in forward direction are obtained. With balanced emissions from the two emitters, the white light emission with very high correlated color temperature of 7308 K as well as CIE coordinates of (0.30, 0.33) is achieved.     

Non-doped red to yellow organic light-emitting diodes with an ultrathin 4-(dicyanomethylene)-2-t-butyl-6(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) layer

In this letter, bright non-doped red to yellow organic light-emitting diodes (OLEDs) with ultrathin 4-(dicyanomethylene)-2-t-butyl-6(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) layer as the emitting layer were fabricated. It was investigated that the effect of the ultrathin DCJTB layer on the electroluminescent (EL) performance of OLEDs. The DCJTB layer was incorporated at different positions in the conventional tris(8-quinolinolato)-aluminum (AlQ)-based devices (ITO/NPB/AlQ/LiF/Al). The emission of DCJTB was dominative in the EL spectra of the devices, in which the position of 0.3 nm DCJTB layer was less than 10 nm from the NPB/AlQ interface. The EL peak emission of DCJTB shifted to blue side as DCJTB position moved gradually from AlQ to NPB layer. The highest brightness of the device with 0.3 nm DCJTB layer inserted into NPB reached 16,200 cd/m² at 15 V, with the CIE coordinates of (0.522, 0.439).     

利用BCP层调节白色磷光有机电致发光器件色度的研究

制备了三种结构的白色有机电致发光器件，通过比较得出：在发光层中间插入2，9-二甲基-4，7-二苯基-1，10-菲咯啉(BCP)能有效控制载流子在不同发光层的分布，进而对器件色度进行调节；而掺杂磷光染料Ir(ppy)₃作敏化剂能有效提高器件的效率. 结构为:氧化铟锡/聚乙烯基咔唑∶N，N′-二(1-萘基)-N，N′-二苯基-1，1′-联苯-4-4′-二胺(30nm)/二-(2-甲基-8-羟基喹啉)-4-联苯酚铝：3.0 wt%2，5，8，11-tetra-tertbutylperylene(TBPe)(30nm)/BCP(5.0nm)/4,4N,N二咔唑基二苯：5.0 wt%Ir(ppy)₃:2.0 wt%红荧烯(15nm)/BCP(10nm)/Mg:Ag的器件色度和效率俱佳. 其在17V工作电压下具有的亮度为4670cd/m²，对应色坐标为(0.31,0.37). 器件具有的最大外量子效率为1.4%，当驱动电压从5.0V升高到17V，器件色坐标严格位于白光色域区内. 关键词： 磷光染料 阻挡层 白光 双发光层     

同时掺杂磷光和荧光染料的白色有机电致发光器件性能研究

以磷光染料Ir(piq)₂(acac)作为发光掺杂剂,掺入空穴传输性主体材料NPB中得到红色发光层,荧光材料TBP掺入到主体CBP中作为蓝色发光层,制备了结构为ITO/NPB/NPB：Ir(piq)₂(acac)/CBP/CBP：TBPe/BCP/ALq/Mg：Ag的双发光层白色有机电致发光器件.其中ALq₃、未掺杂的NPB和CBP及BCP层分别作为电子传输层、空穴传输层和激子阻挡层.实验中通过调节发光层厚度及Ir(piq)_{2关键词： 磷光 激子阻挡层 有机电致发光}     

Optical properties of white organic light-emitting devices fabricated with three primary-color emitters by using organic molecular-beam deposition

White organic light-emitting devices (WOLEDs) with Mg:Ag/Alq₃/Alq₃:DCJTB/Alq₃/DPVBi/α-NPD/ITO and Mg:Ag/Alq₃/DPVBi:DCJTB/Alq₃/DPVBi/α-NPD/ITO structures were fabricated with three primary-color emitters of red, green, and blue by using organic molecular-beam deposition. Electroluminescence spectra showed that the dominant white peak for the WOLEDs fabricated with host red-luminescence Alq₃ and DPVBi layers did not change regardless of variations in the current. The Commission Inernationale de l'Eclairage (CIE) chromaticity coordinates for the two WOLEDs were stable, and the WOLEDs at 40 mA/cm² with luminances of 690 and 710 cd/cm² showed an optimum white CIE chromaticity of (0.33, 0.33). While the luminance yield of the WOLED fabricated with a host red-luminescent Alq₃ emitting layer below 30 mA/cm³ was larger than that of the WOLED fabricated with a DPVBi layer, above 30 mA/cm², the luminance yield of the WOLED fabricated with the DPVBi layer was higher than that of the WOLED with the Alq₃ layer and became more stable with increasing current density. These results indicate that WOLEDs fabricated with a host red-luminescence DPVBi layer without any quenching behavior hold promise for potential applications in backlight sources in full-color displays.     

RGB tricolor produced by white-based top-emitting organic light-emitting diodes with microcavity structure

RGB pixels by microcavity top-emitting organic light-emitting diode (TOLED) is beneficial to both minimizing the loss of light and improving the color purity and the efficiency. Based on the multi-emitting layers, white organic light-emitting diodes (OLEDs) and microcavity TOLEDs were prepared. TOLEDs were fabricated using Ag/ITO as the reflector and adjusting layer, Al/Ag as semi-transparent cathode, Alq:DCJTB/TBADN:TBPe/Alq:C545 as white light emitting layer. By adjusting the thickness of ITO, optical length of cavity and the color of the device have been changed. So we get RGB tricolor devices. The peak wavelengths are 476 nm, 539 nm, 601 nm, Commission Internationale d’Eclairage (CIE) coordinates are (0.133, 0.201), (0.335, 0.567), (0.513, 0.360), FWHM are 32 nm, 50 nm, 73 nm for blue, green and red, respectively.     

基于Ag/Ge/Ag阳极的as

通过在Ag层中引入一层Ge薄膜, 获得了具有低反射率和高反射相移的Ag/Ge/Ag复合阳极, 并制备了基于该阳极的蓝光顶发射有机电致发光器件.阳极高的反射相移使得器件在有机层厚度为100 nm时获得了顶发射蓝光发射, 且阳极较低的反射率减弱了器件内的微腔效应, 使得其电致发光光谱在不同视角下具有良好的稳定性.当Ge的厚度为20 nm时, 器件性能表现最为优良, 最高亮度和最大电流效率分别可达3 612 cd/m²和5.4 cd/A, 且色坐标在视角从0°变化到60°时仅移动了(0.007, 0.006).     

Improving the color purity and efficiency of blue organic light-emitting diodes (BOLED) by adding hole-blocking layer

This work demonstrates the fabrication of a bright blue organic light-emitting diode (BOLED) with good color purity using 4,4′-bis(2,2-diphenylvinyl)-1,1′-biphenyl (DPVBi) and bathocuproine (BCP) as the emitting layer (EML) and the hole-blocking layer (HBL), respectively. Devices were prepared by vacuum deposition on indium tin oxide (ITO)-glass substrates. The thickness of DPVBi used in the OLED has an important effect on color and efficiency. The blue luminescence is maximal at 7670 cd/m² when 13 V is applied and the BCP thickness is 2 nm. The CIE coordinate at a luminance of 7670 cd/m² is (0.165, 0.173). Furthermore, the current efficiency is maximum at 4.25 cd/A when 9 V is applied.     

高效率荧光粉转换型白光有机发光二极管的制备和性能研究

制备了一种荧光粉转换型白光有机发光二级管(pc-WOLEDs),器件由发蓝光的荧光装置和发红光的无机荧光粉Sr₂Si₅N₈∶Eu²⁺颜色转化层(CCL)复合组成,前者通过真空镀膜得到,后者采用旋涂法制备。CCL发射的红光和未被吸收的蓝光复合产生白光,最大发光效率为22.1 cd/A,最大能量效率为11.26 lm/W,外量子效率为10.2%。该pc-WOLEDs的色坐标为(0.32, 0.34),非常接近标准白光(0.33, 0.33)。稳定性实验结果显示,该器件在不同电流密度下表现出了良好的稳定性。     

白光LED用稀土荧光粉的制备和性质

在还原气氛保护下利用高温固相法合成了化学组分为(M₁,M₂)₁₀(PO₄)₆X₂(M₁=Ca,Sr,Ba;M₂=Eu,Mn;X=F,Cl,Br)的可被紫光激发的蓝光、绿光和红光荧光粉,制备了紫光LED芯片+蓝光荧光粉+YAG荧光粉的二基色白光LED;紫光LED芯片+蓝光荧光粉+红光荧光粉的二基色白光LED,以及紫光LED芯片+蓝光荧光粉+绿光荧光粉+红光荧光粉的三基色白光LED。测试了所有制备的白光LED在不同的直流电驱动下的色度坐标、相关色温和显色指数。     

顶发射白光OLED微型显示器的蓝光掺杂特性研究

白光OLED微型显示器在信息显示领域具有重要的应用。采用真空镀膜系统,依次蒸镀Ag/ITO复合薄膜作为阳极结构,共蒸制备Mg∶Ag复合膜作为半透明阴极结构,NPB作为空穴传输材料和黄光主体材料,rubrene作为黄光掺杂料,AND作为蓝光主体料,DSA-Ph作为蓝光掺杂料,Alq3作为电子传输材料,以结构和工艺简化的蓝、黄光互补色来实现白光,通过共蒸发形式制备了结构为Ag/ITO/NPB/NPB∶rubrene（1.5%）/ADN∶DSA-Ph（x%/x=2,5,8）/Alq3/Mg∶Ag的白光OLED微型显示器,利用由Photo Research PR655光谱仪、Keithley 2400程控电源组成的光谱测试系统对器件的光电性能进行表征,研究了蓝光掺杂比对白光OLED微型显器性能的影响。结果表明,随着蓝光掺杂比的增加,白光OLED微型显示器的亮度先增加后降低,蓝光、黄光峰位有所偏移,色坐标发生一定的漂移,蓝光色纯度增加,可通过调控发光材料掺杂比实现白光OLED微型显示器性能的可控制备。初步优化获得的蓝、黄混合白光OLED微型显示器的器件,当驱动电压为5.0 V时,器件亮度达到3 679 cd·m-2,CIE坐标为（0.263,0.355）。     

一种多层白色磷光有机电致发光器件的制备及性能研究

制备了一种结构为ITO/NPB/NPB:Ir(piq)₂(acac)/CBP:TBPe/BAlq:rubrene/BAlq/Alq₃/Mg:Ag的白色磷光有机电致发光器件.其中空穴传输型主体NPB掺杂磷光染料Ir(piq)₂(acac)作为红色发光层,双载流子传输型主体4,4′-N,N′-dicarbazole-biphenyl (CBP)掺杂TBPe作为蓝色发光层,电子传输型主体材料BAlq掺杂rubrene作为绿色发光层.以上发光层夹于 关键词： 电致发光 磷光染料 异质结 白光     

Enhancement of performance for blue organic light emitting devices by utilizing an adjustable chromaticity layer

An adjustable chromaticity layer was successfully applied to a TBADN-based blue organic light-emitting device (BOLED) for improving chromaticity and luminance efficiency. The device was constructed by sandwiching an ultrathin [DPVBi: BCzVB] layer between hole-transport layer and primary emission layer. The optimized device gives the Commission Internationale de I’éclairage (CIE) color coordinates of (0.166, 0.201) at the current density of 20 mA/cm² and a maximum luminance efficiency of 8.43 cd/A at the driving voltage of 11 V.     

High efficiency small molecule white organic light-emitting devices with a multilayer structure

In this paper, a new white organic light-emitting device (WOLED) with multilayer structure has been fabricated. The structure of devices is ITO/N, N-bis-(1-naphthyl)-N, N^′-diphenyl-1, 1′-biphenyl-4, 4′-diamine (NPB) (40 nm)/NPB: QAD (1%): DCJTB (1%) (10 nm) /DPVBi (10 nm) /2, 9-dimethyl, 4, 7-diphenyl, 1, 10-phenanthroline (BCP) (d nm)/tris-(8-hydroxyquinoline) aluminium (Alq₃)(50-d nm)/LiF (1 nm)/Al (200 nm). In our devices, a red dye 4-(dicyanomethylene)-2-t-butyl-6 (1, 1, 7, 7-tetramethyl julolidyl-9-enyl)-4H-pyran (DCJTB) and a green dye quinacridone (QAD) were co-doped into NPB. The device with 8 nm BCP shows maximum luminance of 12 852 cd/m² at 20 V. The current efficiency and power efficiency reach 9.37 cd/A at 9 V and 3.60 lm/W at 8 V, respectively. The thickness of the blocking layer permit the tuning of the device spectrum to achieve a balanced white emission with Commission International de’Eclairage (CIE) chromaticity coordinates of (0.33,0.33). The CIE coordinates of device change from (0.3278, 0.3043) at 5 V to (0.3251, 0.2967) at 20 V that are well in the white region, which is largely insensitive to the applied bias.     

White organic electroluminescence from fluorescent bis (2-(2-hydroxyphenyl) benzoxazolate)zinc doped with phosphorescent material

Efficient white electroluminescence has been obtained by using an electroluminescent layer comprising of a blue fluorescent bis (2-(2-hydroxyphenyl) benzoxazolate)zinc [Zn(hpb)₂] doped with red phosphorescent bis (2-(2′-benzothienyl) pyridinato-N,C^3′)iridium(acetylacetonate) [Ir(btp)₂acac] molecules. The color coordinates of the white emission spectrum was controlled by optimizing the concentration of red dopant in the blue fluorescent emissive layer. Organic light-emitting diodes were fabricated in the configuration ITO/α-NPD/Zn(hpb)₂:0.01 wt%Ir(btp)₂acac/BCP/Alq₃/LiF/Al. The J-V-L characteristic of the device shows a turn on voltage of 5 V. The electroluminescence (EL) spectra of the device cover a wide range of visible region of the electromagnetic spectrum with three peaks around 450, 485 and 610 nm. A maximum white luminance of 3500 cd/m² with CIE coordinates of (x, y=0.34, 0.27) at 15 V has been achieved. The maximum current efficiency and power efficiency of the device was 5.2 cd/A and 1.43 lm/W respectively at 11.5 V.     

Efficient polymer white-light-emitting diodes with a single-emission layer of fluorescent polymer blend

Efficient polymer white-light-emitting diodes (WPLEDs) have been fabricated with a single layer of fluorescent polymer blend. The device structure consists of ITO/PEDOT/PVK/emissive layer/Ba/Al. The emissive layer is a blend of poly(9,9-dioctylfluorene) (PFO), phenyl-substituted PPV derivative (P-PPV) and a copolymer of 9,9-dioctylfluorene and 4,7-di(4-hexylthien-2-yl)-2,1,3-benzothiadiazole (PFO-DHTBT), which, respectively, emits blue, green and red light. The emission of pure and efficient white light was implemented by tuning the blend weight ratio of PFO: P-PPV: PFO-DHTBT to 96:4:0.4. The maximum current efficiency and luminance are, respectively, 7.6 cd/A at 6.7 V and 11930 cd/m² at 11.2 V. The CIE coordinates of white-light emission were stable with the drive voltages.