新型高效红色磷光OLED器件

使用R-4B新型红色磷光染料作为掺杂剂,制作了结构为ITO/MoO3(10)/NPB(40)/TCTA(10)/CBP∶R-4B(x)/BCP(10)/Alq3(40)/LiF/Al的红色磷光器件,结合TCTA和BCP(电子和空穴阻挡材料),通过调节R-4B的掺杂比例,对器件的发光性能和发光机理进行了研究。结果表明,掺杂比例为6%时,得到光效和颜色稳定性较好的器件。在电压为4V时,电流密度为0.045mA/cm2,亮度为3.57cd/m2,最大电流效率为19.48cd/A;在电压分别为5、10和15V时,色坐标分别为(0.60,0.35)、(0.64,0.34)、(0.64,0.35)。分析认为,一方面,R-4B的发光机理主要有主体材料CBP对R-4B的能量传递及载流子直接注入R-4B形成激子;另一方面,TCTA和BCP的作用为对发光层内载流子、激子的阻挡及使空穴、电子更有效注入发光层。     

空穴注入层MoO_3厚度对蓝绿色磷光OLED发光特性的影响

以mCP为磷光主体材料,BGIr1为蓝绿色磷光掺杂材料,MoO3为空穴注入材料,制备5种不同厚度的MoO3蓝绿色磷光有机电致发光器件(OLED),并研究不同厚度MoO3空穴注入层对蓝绿色磷光OLED发光特性的影响。所制器件结构为ITO/MoO3(x nm)/NPB(40nm)/mCP∶BGIr1(30nm,18%)/BCP(10nm)/Alq3(20nm)/LiF(1nm)/Al(100nm),其中18%为发光层中BGIr1的掺杂量(质量分数),x为空穴注入层MoO3的厚度。研究结果表明,本实验制备器件空穴注入层MoO3的最佳厚度为20nm。当电压为13V时,MoO3厚度为20nm器件获得最大亮度为8 617cd/cm2,当电流密度为20mA/cm2时,器件获得最大发光效率为5.7cd/A。器件在488和512nm处获得两个主发射峰,发光颜色稳定,CIE坐标为(0.19,0.21)。     

高效稳定性有机黄光电致发光器件

主要通过红绿磷光材料R-4B和GIr1掺杂的方法,制备了黄光OLED器件,器件结构为ITO/MoO3(X)/NPB(40nm)/TCTA(10nm)/CBP:GIr1 14%:R-4B2%(30nm)/BCP(10nm)/Alq3(40nm)/LiF(1nm)/Al(100nm),TCTA和BCP分别为电子和空穴阻挡材料,同时结合TCTA和BCP对载流子的高效阻挡作用,研究了MoO3对器件效率和稳定性的影响。发现当增加MoO3的厚度为90nm时,在较大的电压范围内,器件都具有较高的效率和色坐标稳定性。在电流密度为7.13mA/cm2时,器件达到最高电流效率29.2cd/A,亮度为2081cd/m2;电流密度为151.7mA/cm2时,获得最高亮度为24430cd/m2,电流效率为16.0cd/A;器件色坐标稳定性较好,当电压为5、10、15V时,色坐标分别为(0.5020,0.4812)、(0.4862,0.4962)、(0.4786,0.5027)。器件性能的改善主要归因于载流子注入与传输的平衡以及阻挡层对发光区域的有效限定。     

PtOEP掺杂Alq3有机发光器件的能量传递

研究了高效磷光染料八乙基卟啉铂(PtOEP)掺杂于主体材料八羟基喹啉铝(Alq3)体系中PtOEP、Alq3之间的能量传输机制.分别以PtOEP掺杂和未掺杂的Alq3膜作为发光层制作有机发光器件(OLED),改变掺杂浓度,检测器件电致发光(EL)光谱的变化.经分析,在5%、10%、20%三种掺杂浓度中,10%掺杂浓度能量传递效果最好.通过对掺杂和未掺杂器件电流密度-电压、亮度-电压数据检测,计算外量子效率,在低电流密度(《7mA/cm2)驱动下掺杂器件外量子效率是未掺杂器件的5倍.     

水溶胶CdSe纳米复合器件电致发光特性的研究

以巯基乙酸为稳定剂在水相中制备了水溶胶CdSe纳米晶,透射电子显微镜表明了纳米晶的形态和尺寸大小.用表面活性剂将CdSe纳米晶从水相中转移到有机相中,将其与具有空穴传输性能的聚合物PVK互溶在一起作为电致发光器件的发光层,以Alq3作为电子传输层,在发光层与Alq3之间加入了空穴阻挡层BCP制备了多层电致发光器件,研究了不同CdSe/PVK配比下水溶胶CdSe纳米复合器件的电致发光特性,结果发现随着水溶胶CdSe纳米晶在纳米复合物中所占比例的降低,电致发光器件的发光强度有所提高,起亮电压有所降低.     

新型钙镁铝合金阴极对红光OLED性能的影响研究

采用不同比例的Ca/Mg/Al合金和纯Ca/Al合金阴极分别制备结构为ITO/Mo O_3(30nm)/NPB(40nm)/TCTA(10nm)/CBP:R-4B(30nm)/TPBI(10nm)/Alq3(30nm)/Ca:Mg(X%):Al(100nm)和ITO/Mo O3(30nm)/NPB(40nm)/TCTA(10nm)/CBP:R-4B(30nm)/TPBI(10nm)/Alq3(30nm)/Ca:Al(100nm)的红光有机电致发光二极管(OLED)器件及其对应的电子型器件,研究了阴极材料对器件的影响。结果发现,Ca/Mg/Al合金阴极可以提高阴极发射电子能力。当Mg掺杂质量比为20%时,器件具有最优性能,在电压为13 V时,发光亮度为10250 cd/m2,电流密度为57.099 m A/cm2,最大电流效率为18.8426 cd/A,效率较高且滚降比较平缓。原因为载流子注入比较平衡,形成了较多的激子。     

基于N-苯基咔唑的红色有机电致发光材料

设计合成了一种N-苯基咔唑的衍生物:3-2-(3,3-二腈基亚甲基-5,5-二甲基-1-环己烯基)乙烯基-N-苯基-咔唑(PNCa-2CN).PNCa-2CN的甲醇溶液光致发光光谱和固体膜光致发光光谱峰值分别位于598nm和660nm.以PNCa-2CN作为红色发光材料掺杂在Alq3中,制备了结构为ITO/NPB/Alq3:PNCa-2CN(5%)/Alq3/Mg:Ag/Ag的具有较高发光效率的红色有机电致发光器件,器件的发光峰值为600nm,在外加20V直流电压时达到2372cd·m-2的发光亮度,100mA·cm-2和20mA·cm-2其亮度分别为323cd·m-2和64cd·m-2,器件最大流明效率达到1.3lm·W-1.     

基于Alq3及蒽类衍生物的微腔顶发射有机发光器件

制做了具有微腔结构的绿色和蓝色有机顶发射电致发光器件.利用Alqs和TBADN:3%DSAPh材料为发光层,Ag为阳极反射层,ITO为腔长调节层,Al/Ag为半透明阴极,电极的透射率在30%左右.通过改变ITO层的厚度,Alq3器件得到了不同颜色的发光光谱,实现了对光谱的调节作用;TBADN:3%DSAPh器件获得了纯度较高的蓝色发光光谱,色坐标为(0.141,0.049),半高宽为17nm发光光谱,实现了窄带发射.文章对微腔顶发射器件的发射强度和发光光谱半高宽的结果进行了分析.     

9,9'-联葸的合成及其白色有机电致发光器件的研制

详细叙述了利用9-溴蒽为原料制备高纯蓝色有机发光材料9,9'-联二蒽的方法,在研究了此材料和黄光染料Rubrene发光特性的基础上,采用高效的荧光染料Rubrene作为掺杂剂掺杂在母体材料9,9'-联蒽中,制备了单发光层结构的有机电致发光器件.当掺杂摩尔分数为1.0%,驱动电压为12V时,器件得到了近白色发光(色坐标x=0.328,y=0.342).在驱动电压为23V时,器件的亮度达到了7843cd/m2,在驱动电压为13V时,器件的效率达到了3.45cd/A.     

红荧烯衍生物的红光电致发光器件及其在照明中的应用

合成了一种红荧烯的衍生物,2-甲酰基红荧烯作为一种红光掺杂剂,掺杂在N,N-diphenyl-N,N-bis 1-naphthyl–1,1-biphenyl-4,4-diamine(NPB)中制备的电致发光器件,发射峰位于598nm,电流效率为2.1cd/A。用这个红光掺杂系统制备了一个白光电致发光器件,在白光器件中,2-甲酰基红荧烯,八-羟基喹啉铝(Alq3),以及NPB分别组成了白光中的红、绿以及蓝的发光成分,获得了一个白光器件,该器件显色指数高达89.8,在11V时,色坐标达(0.33,0.33),最大亮度为5000cd/m2以及最大发光效率为4.7cd/A。这些性能参数表明这个白光器件具有潜在的照明应用。另外,还讨论了器件的结构设计以及电致发光过程及机理。     

Study on energy relation between blue and red emissive layer of organic light-emitting diodes by inserting spacer layer

In this paper, energy relation between blue emissive layer (blue-EML) and red emissive layer (red-EML) in organic light-emitting diodes based on blue-emitting and red-emitting phosphorescent dopants, bis(3,5-difluoro-2-(2-pyridyl)phenyl-(2-carboxypyridyl) iridium III (Firpic) and bis(2-(2′-benzo[4,5-α]thienyl)pyridinato-N,C3′)iridium(acetylacetonate) (Btp₂Ir(acac)), was studied. Two phosphorescent dopants, Firpic and Btp₂Ir(acac), were co-doped in the single emissive layer, and the results exhibit complete energy transfer from Firpic to Btp₂Ir(acac). Then, Firpic and Btp₂Ir(acac) were doped into blue-EML and red-EML, separately. By inserting 4,4′-bis(N-carbazolyl)biphenyl (CBP) spacer between blue- and red-EML, energy relation between blue- and red-EML was researched. The results of this work reveal that, CBP spacer may strengthen energy transfer between blue- and red-EML. The reason is that CBP triplets at blue-/red-EML interface can transfer their energies to both CBP molecules of red-EML and Firpic molecules of blue-EML in spacer-without devices, while CBP triplets in the spacer can transfer their energies only to CBP molecules of red-EML. Therefore, energy flow from blue- to red-EML is strengthened because of the avoidance of energy transfer from CBP triplets in the spacer to Firpic molecules of blue-EML, leading to the relative enhancement of red emission in CBP-spacer devices.     

Enhanced efficiency in mixed host red electrophosphorescence devices

Enhanced efficiency of red phosphorescent organic light-emitting devices is observed by using a bis[2-(2′-benzothienyl)pyridinato-N,C^3′] iridium(acetylacetonato) doped 4,4′-N,N′-dicarbazole-biphenyl (CBP) and 1,3,5-tris(N-phenylbenzimidazole-2-yl)benzene (TPBI) mixed host emitting layer. The CBP:TPBI mixed host device shows a maximum external quantum efficiency of 9.1%, which is dramatically improved compared to that of the CBP (6.6%) and TPBI (5.4%) single host devices. Such a mixed host strategy can also be exploited in red phosphor dibenzo[f,h]quinoxaline iridium (acetylacetonate) doped devices. Investigations reveal that the position of charge carrier recombination zone of the mixed host devices predominantly locates in the electron blocking layer/emitting layer interface. The efficiency enhancement is attributed to the optimized hole and electron injection balance and hence increased charge carrier recombination rate in the emitting layer.     

Organic light emitting devices with doped electron transport and hole blocking layers

This study reports on heterostructure OLEDs with n-type molecularly doped electron transport layer and hole blocking layer. The influence of doping on the operating voltage and on light emission performances was investigated. The n-type doping molecule is 2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (PBD) dispersed into either an 8-(hydroquinoline) aluminum (Alq) electron transport layer (ETL) or a 2,9-Dimethyl-4,7-diphenyl-1,10-phenanthroline (Bathocuproine BCP) hole blocking layer (HBL). The typical device structure is glass substrate/indium tin oxide/PEDOT/TPD–F4-TCNQ/Alq–DCM/BCP/Alq/Mg–Ag where Poly(3,4)ethylenedioxythiophene/Polystyrenesulphonate (PEDOT/PSS) is a hole injecting layer, TPD–F4-TCNQ is a hole transport layer (HTL) made of N,N′-Bis(3-methylphenyl)-N,N′-diphenylbenzidine (TPD) doped with 2 wt.% of 2,3,5,6-tetrafluoro-7,7,8,8-tetracyano-quinodimethane (F4-TCNQ) and Alq–DCM is the emitting layer (EML) made of Alq doped with 2 wt.% of 4-dicyanomethylene-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran (DCM) orange dye. The modified cathode consists in a combination of a BCP HBL and an Alq ETL where BCP or/and Alq were doped with PBD. Lowest operating voltage (3 V for a luminance of 10 Cd/m²) and brightest devices (6000 Cd/m²) were obtained with a hole blocking bilayer made of BCP doped with 28 wt.% deposited onto an undoped BCP (each one being 5 nm thick). Adding an undoped Alq layer improved the device current efficiency (4 Cd/A) but is detrimental to the operating voltage (6 V for a luminance of 10 Cd/m²). In the absence of real n-type doping with organic molecules, our results point out that the design of molecular doped injection layer at the cathode will need for a compromise between high luminance and efficiency on one hand and low operating voltage on the other hand.     

Red phosphorescent organic light-emitting diodes based on the simple structure

We demonstrated that the simple layered red phosphorescent organic light-emitting diodes (OLEDs) are possible to have high efficiency, low driving voltage, stable roll-off efficiency, and pure emission color without hole injection and transport layers. We fabricated the OLEDs with a structure of ITO/CBP doped with Ir(pq)2(acac)/BPhen/Liq/Al, where the doping concentration of red dopant, Ir(pq)2(acac), was varied from 4% to 20%. As a result, the quantum efficiencies of 13.4, 11.2, 16.7, 10.8 and 9.8% were observed in devices with doping concentrations of 4, 8, 12, 16 and 20%, respectively. Despite of absence of the hole injection and transport layers, these efficiencies are superior to efficiencies of device with hole transporting layer due to direct hole injection from anode to dopant in emission layer.     

调制掺杂ZnMgO/ZnO异质结构中的二维电子气

基于调制掺杂的ZnMgO/ZnO异质结构模型,通过自洽求解一维泊松-薛定谔方程,研究了掺杂浓度、空间层厚度对ZnMgO/ZnO异质界面处二维电子气(2DEG)的分布、面密度等性质的影响。结果表明:ZnO沟道中的二维电子气主要来源于极化效应诱生的电子和掺杂层转移的电子,通过改变掺杂浓度和空间层厚度可以有效地调控异质结中的二维电子气。采取的研究方法和所得结果可以为ZnO基异质结构及相关器件的构筑提供基础。     

Pentafluorophenoxy boron subphthalocyanine as a fluorescent dopant emitter in organic light emitting diodes

A fluorinated phenoxy boron subphthalocyanine (BsubPc) is shown to function as a fluorescent dopant emitter in small molecule organic light emitting diodes (OLEDs). Narrow electroluminescence (EL) emission with a full width at half-maximum of ～30 nm was observed regardless of the host used, indicating that this narrow EL is intrinsic to the BsubPc molecule. A bathochromic shift and the growth of a new EL peak at higher wavelengths with increasing doping concentration were found to be a result of molecular aggregation. Excitation of BsubPc by direct charge trapping as well as Fo?rster resonant energy transfer were shown using different host molecules. A maximum efficiency of 1.5 cd/A was achieved for a 4,4'-N,N'-dicarbazole-biphenyl (CBP) host.     

Enhancements in device efficiency of poly(3-hexylthiophene): [6,6]-phenyl C61-butyric acid methyl ester based solar cells with incorporation of bathocuproine

The overall enhancement of poly(3-hexylthiophene): [6,6]-phenyl C61-butyric acid methyl ester based organic solar cell with a thin layer of bathocuproine (BCP) inserted between active layers and aluminum (Al) cathodes was investigated. X-ray and ultraviolet photoemission spectroscopy show that no reaction occurs at the active layer/BCP interface and 2 nm of BCP could effectively suppress the chemical reactions between Al and active layers. Atomic force microscope images also indicate that BCP layers can provide smoother contact surfaces with Al cathodes and suppress the generation of shunt leakage, resulting in larger V_oc and better power conversion efficiency of devices.     

Initial biocompatibility and enhanced osteoblast response of Si doping in a porous BCP bone graft substitute

Granular shape biphasic calcium phosphate (BCP) bone grafts with and without doping of silicon cations were evaluated in regards to biocompatibility and MG-63 cellular response. To do this we studied Cellular cytotoxicity, cellular adhesion and spreading behavior and cellular differentiation with alizarin red S staining. Gene expression in MG-63 cells on the implanted bone substitutes was also examined at different time points using RT-PCR. In comparison, the Si-doped BCP granule showed more cellular viability than the BCP granule without doping in MTT assay. Moreover, cell proliferation was much higher when Si doping was employed. The cells grown on the silicon-doped BCP substitutes had more active filopodial growth with cytoplasmic webbing that proceeded to the flattening stage, which was indicative of well cellular adhesion. When these cells were exposed to Si-doped BCP granules for 14 days, well differentiated MG-63 cells were observed. Osteonectin and osteopontin genes were highly expressed in the late stage of differentiation (14 days), whereas collagen type I mRNA were found to be highly expressed during the early stage (day 3). These combined results of this study demonstrate that silicon-doped BCP enhanced osteoblast attachment/spreading, proliferation, differentiation and gene expression.     

Photo/electroluminescence properties of an europium (III) complex doped in 4,4′-N,N′-dicarbazole-biphenyl matrix

The photoluminescence properties of one europium complex Eu(TFNB)₃Phen (TFNB = 4,4,4-trifluoro-1-(naphthyl)-1,3-butanedione, Phen = 1,10-phenanthroline) doped in a hole-transporting material CBP (4,4′-N,N′-dicarbazole-biphenyl) films were studied. A series of organic light-emitting devices (OLEDs) using Eu(TFNB)₃Phen as the emitter were fabricated with a multilayer structure of indium tin oxide, 250 Ω/square)/TPD (N,N′-diphenyl-N,N′-bis(3-methyllphenyl)-(1,1′-biphenyl)-4,4′-diamine, 50 nm)/Eu(TFNB)₃phen (x): CBP (4,4′-N,N′-dicarbazole-biphenyl, 45 nm)/BCP (2,9-dimethyl-4,7-diphenyl-l,10 phenanthroline, 20 nm)/AlQ (tris(8-hydroxy-quinoline) aluminium, 30 nm)/LiF (1 nm)/Al (100 nm), where x is the weight percentage of Eu(TFNB)₃phen doped in the CBP matrix (1-6%). A red emission at 612 nm with a half bandwidth of 3 nm, characteristic of Eu(III) ion, was observed with all devices. The device with a 3% dopant concentration shows the maximum luminance up to 1169 cd/m² (18 V) and the device with a 5% dopant concentration exhibits a current efficiency of 4.46 cd/A and power efficiency of 2.03 lm/W. The mechanism of the electroluminescence was also discussed.     

Fabrication and Sintering Behavior of Zinc-Doped Biphasic Calcium Phosphate Bioceramics

Dense bioceramics with improved mechanical properties have been prepared using sol–gel derived zinc doped biphasic calcium phosphate (BCP) powders. Zinc concentration was varied in the range of 0,1, 2, 4, 5, 10, and 15 mol%. The compaction of the powders followed by sintering provided the dense ceramics. The effects of zinc concentration doped and sintering temperature on phase stability and mechanical characteristics were examined. The presence of Zn changed the phase of dense BCP, leading to improved mechanical properties. Zn free BCP attained the highest density of only 92.6% after 1400°C sintering, equally achieved by 4 mol% Zn-doped BCP at a lower temperature of 1200°C. It is presumed that the steady increase in the compact density up to 4 mol% zinc incorporation was contributed by progressive consolidation in the BCP structure, but the density dropped again from 5 mol% until 15 mol% due to low density β-tricalcium phosphate phase formation. This study showed that Zn doping was effective in producing high strength dense BCP with 3.40 GPa hardness and 1.43 MPa · m^1/2 fracture toughness.