Diphenylvinyl)-1,1′-biphenyl Research Articles

Organic light-emitting devices based on 4,4’-bis(2,2’-diphenyl vinyl)-1,1’-biphenyl as a spacer between dual ultrathin layers

White organic light-emitting devices (WOLEDs) were fabricated by using a highly blue fluorescent dye of 4,4’-bis(2,2’-diphenyl vinyl)-1,1’-biphenyl (DPVBi) and a red fluorescent dye of 5H-benzo[ij] quinolizin-9-yl) ethenyl]-4H-pyran-4-ylidene] propane-dinitrile (DCM2), together with a green fluorescent dye of 10-(2-benzothiazolyl)-2,3,6,7-tetrahydro-1,1,7,7-tetramethyl-1H,5H,11H-(1)-benzopyroyran-o(6,7-8-i,j) quinolizin-11-one (C545T). The multilayer WOLEDs does not involve the doping process. The structure of the device is indium tin oxide (ITO)/4,4’,4”-tris{N,-(3-methylphenyl)-N-phenylamin}triphenylamine (m-MTDATA) (55 nm)/ N,N’-bis-(1-naphthyl)-N,N’-diphenyl-1,1’-biph-enyl-4,4’-diamine (NPB) (10 nm)/ DPVBi (8 nm)/ C545T (x nm)/ DPVBi (5 nm)/ DCM2 (y nm)/ tris- (8-hydroxyquinoline) aluminum (Alq3) (60nm)/ LiF (1 nm)/ Al, where the DPVBi is introduced as a spacer. By changing the thicknesses of dual ultrathin layers of C545T and DCM2, the WOLED is obtained. When x=y=0.05, the Commission Internationale de 1’Eclairage (CIE) coordinates of the device change from (0.262 6, 0.351 4) at 4 V to (0.214 7, 0.269 3) at 12 V that are well in the white region. Its maximum luminance is 41400 cd/m2 at 13 V, and the maximum current efficiency and the maximum power efficiency are 7.95 cd/A at 6 V and 5.37 lm/W at 5 V, respectively.

Flexible white phosphorescent organic light emitting diodes based on multilayered graphene/PEDOT:PSS transparent conducting film

A double-layered graphene/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) conductive film was prepared, in which the PEDOT:PSS layer was obtained by using spray-coating technique. A flexible white phosphorescent organic light-emitting devices based on the graphene/PEDOT:PSS conductive film was fabricated. Phosphorescent material tris(2-phenylpyridine) iridium (Ir(ppy)3) and the fluorescent dye 5,6,11,12-tetraphenylnapthacene (Rubrene) were co-doped into 4,4′-N,N′-dicarbazole-biphenyl (CBP) host. N,N′-diphenyl-N,N′-bis(1-naphthyl)-(1,1′-biphenyl)-4,4′-diamine (NPB) and 4,7-diphenyl-1,10-phenanthroline (Bphen) were used as hole-transporting and electron-transporting layer, respectively, and 4,4′-bis(2,2′-diphenylvinyl)-1,1′-biphenyl (DPVBi) was used as blue light-emitting layer. The device presented pure white light emission with a Commission Internationale De I’Eclairage coordinates of (0.31, 0.33) and exhibited an excellent light-emitting stability during the bending cycle test with a radius of curvature of 10mm.

High-Color-Quality Blue Top-Emitting Organic Light-Emitting Diodes with Enhanced Contrast Ratio

On the basis of a Ag:MoO3 anode, we fabricated blue top-emitting organic light-emitting diodes with enhanced contrast ratio. After doping with MoO3, the reflectivity of Ag anode was reduced by a great ratio. Owing to the decrease in the anode reflectivity, the total reflectivity of the devices also decreased. Accordingly, the contrast ratio of the devices was enhanced. In addition, a purer blue emission was obtained from devices with a low-reflectivity anode. We obtained a blue emission with a spectra peak at 436 nm from top-emitting devices based on 4,4'-bis(2,2'-diphenylvinyl)-1,1'-biphenyl (DPVBi). The emission spectra of the top-emitting devices with a Ag:MoO3 anode were very stable at different view angles.

超薄插入法实现的理想白色有机电致发光器件

By using typical luminescent materials,4,4′-bis(2,2′-diphenylvinyl)-1,1′-biphenyl(DPVBi) and 5,6,11,12-tetraphenylnaphthacene(Rubrene) as a blue and orange emitter,respectively,a highly efficient bright nondoped white electroluminescent device with low driving voltage and ideal chromaticity is fabricated.The turn-on voltage,maximum current efficiency are 3.1 V,6.7 cd/A(luminous efficacy of 5.5 lm/W,external quantum efficiency of 2.8%),respectively.Commission Internationale de l'Eclairage(CIE) co-ordinates are at ideal equal-energy white point(0.33,0.33).The achievement of excellent white emission is attributed to realizing perfect ratio of energy transfer from DPVBi to Rubrene by tuning distance from NPB/DPVBi interface to Rubrene.

Flexible White Organic Light-Emitting Devices with a Porous Red Polymer Layer and a Blue Small Molecular Layer Utilizing a Phase Separation of Blended Polymer

Flexible white organic light-emitting devices (WOLEDs) with an emitting layer consisting of a porous red poly(2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylenevinylene) (MEH-PPV) polymer layer and a blue 4,4'-bis(2,2'-diphenylvinyl)-1,1'-biphenyl (DPVBi) small molecular layer were fabricated on polyethylene terephthalate substrates. The current density of the flexible WOLEDs fabricated with a blend layer formed with a higher spincoating speed was significantly higher than that of a device fabricated with a lower spincoating speed, due to the higher pore density. The ratio between the red and the blue color peak intensities of the electroluminescence spectra for the flexible WOLEDs with a porous red MEH-PPV polymer layer and a blue DPVBi small molecular layer was controlled by the spincoating speed of the blend layer.

Influence of active layer thickness on the performance of distyrylarylene derivative blue organic light-emitting device

Thickness of emissive layer in organic electroluminescent device is one of the important factors affecting the device performance. In this report, a blue electroluminescent device with an active layer of 4, 4'-bis(2, 2'-diphenylvinyl) -1, 1'- biphenyl (DPVBi) is fabricated. The device performance varies with the thickness of DPVBi. With the increase of the DPVBi thickness between 1050 nm, the device luminance and efficiency at the same current density first increase and then decrease, the device with a DPVBi thickness of 40 nm exhibits the highest luminance of 15840 cd/m2 and a maximum external quantum efficiency of 3.2%, with Commission Internationale de l'Eclairage (CIE) co-ordinates being (0.15, 0.15). The luminescent spectral red shift and the color purity deteriorate when the thickness is over 40 nm, which can be attributed to a result of microcavity effect. In the meantime, the analysis from experimental results shows that the exciton diffusion length in DPVBi is between 2030 nm.

6,6]-Phenyl C61 Butyric Acid Methyl Ester-Polymer Nanocomposite: A Good Material Platform for Organic Light-Emitting Diodes

PCBM-polymer nanocomposites [[6,6]-Phenyl C61 butyric acid methyl ester (PCBM):Poly(9-vinylcarbazole) (PVK)] were prepared by dissolving them in chloroform. Photophysical properties were studied first, and then the hole-only devices were fabricated to study the hole-transporting properties. The specially designed organic light-emitting diodes (OLEDs) with the structure of indium tin oxide (ITO)/PCBM:PVK (x wt%, approximately 40 nm)/4,4'-bis(2,2'-diphenylvinyl)-1,1'-biphenyl (DPVBi) (30 nm)/Tris-(8-hydroxyquinoline)aluminum (Alq3) (30 nm)/lithium fluoride (LiF) (1 nm)/Al were fabricated to verify the transport properties of the nanocomposites. Finally, the nanocomposites were applied in the Alq3-based OLEDs as a hole-transporting layer. A significant improvement was observed in OLEDs when the nanocomposites were used to replace the conventional pristine PVK.

Solution-processed white organic light-emitting diodes with mixed-host structures

Efficient white light-emitting diodes (WOLEDs) were fabricated with a solution-processed single emission layer composed of a molecular and polymeric material mixed-host (MH). The main host used was a blue-emitting molecular material of 4,4′-bis(2,2′-diphenylvinyl)-1,1′-biphenyl (DPVBi) and the assisting host used was a hole-transport-type polymer of poly(9-vinylcarbazole) (PVK). By co-doping 4,4′-bis[2-(4-( N,N-diphenylamino)phenyl)vinyl]biphenyl and 5,6,11,12-tetraphenylnaphacene into the MH, the performances of the fabricated devices made with different mixing ratio of host materials were investigated, and were to depend on the mixing ratios. Under the optimal PVK:DPVBi ratio (3:7), we achieved a maximum luminance of 14 110 cd/m 2 and a maximum current efficiency of 9.5 cd/A. These improvements were attributed to the MH structure, which effectively improved the thermal stability of spin-coated film and enhanced the hole-injection/transporting properties of WOLEDs.

Low voltage red phosphorescent organic light-emitting devices with triphenylphosphine oxide and 4,4′-bis(2,2′-diphenylvinyl)-1,1′-biphenyl electron transport layers

We have developed red phosphorescent organic light-emitting devices operating at low voltages by using triphenylphosphine oxide (Ph 3PO) and 4,4′-bis(2,2′-diphenylvinyl)-1,1′-biphenyl (DPVBi) electron transport layers. 4,4′-bis( N-carbazolyl)-1,1′-biphenyl (CBP) and tris-(1-phenylisoquinolinolato- C 2, N) iridium(III) [Ir(piq) 3] were used as host and guest materials, respectively. Small voltage drops across the electron transport layers and direct injection of holes from 4,4′,4″-tris[ N-(2-naphthyl)- N-phenyl-amino]-triphenylamine (2-TNATA) hole transport layer into the Ir(piq) 3 guests are responsible for the high current density at low voltage, resulting in a high luminance of 1000 cd/m 2 at low voltages of 2.8–3.0 V in devices with a structure of ITO/2-TNATA/CBP:Ir(piq) 3/DPVBi/Ph 3PO/LiF/Al.

White organic light-emitting devices with a bipolar transport layer between blue fluorescent and yellow phosphor-sensitized-fluorescent emitting layers

We report white organic light-emitting devices (WOLEDs) based on 4,4′-bis(2,2′-diphenylvinyl)-1,1′-biphenyl (DPVBi) and phosphorescence sensitized 5,6,11,12-tetraphenylnaphthacene (rubrene). By introducing a bipolar transport 4,4′-N,N′-dicarbazole-biphenyl (CBP) layer between the fluorescent and the phosphor-sensitized-fluorescent layers, additional light emission from the phosphorescence sensitized layer is observed. This can be attributed to the elimination of the Dexter energy transfer between these two emitters. White emission with Commission International de L’Eclairage coordinates of (0.22,0.33) and a maximum luminance of 22,360 cd/m 2 were obtained. The maximum current efficiency can reach 10.7 cd/A.

HTL:EML(DPVBi:NPB)층의 조성비 변화에 따른 청색 유기 발광 소자 개발

The structure of organic light-emitting diodes(OLEDs) with typical heterostructure consists of anode, hole injection layer, hole transport layer, light-emitting layer, electron transport layer, electron injection layer, and cathode. 4,4bis[N-(1-napthyl)-N-phenyl-amino]-biphenyl(NPB) used as a hole transport layer and 4'4-bis(2,2'-diphenyl vinyl)-1,1'-biphenyl(DPVBi) used as a blue light emitting layer were graded-mixed at selected ratio. Interface at heterojunction between the hole transport layer and the elecrtron transport layer restricts carrier's transfer. Mixing of the hole transport layer and the emitting layer reduces abrupt interface between the hole transport layer and the electron transport layer. The operating voltage of OLED devices with graded mixed-layer structure is 2.8 V at 1 <TEX>$cd/m^2$</TEX> which is significantly lower than that of OLED device with typical heterostructure. The luminance of OLED devices with graded mixed-layer structure is 21,000 <TEX>$cd/m^2$</TEX> , which is much higher than that of OLED device with typical heterostructure. This indicates that the graded mixed-layer enhances the movement of carriers by reducing the discontinuity of highest occupied molecular orbital(HOMO) of the interface between hole transport layer and emitting layer.

Low voltage organic light-emitting devices with triphenylphosphine oxide layer

We have developed low voltage driving organic light-emitting devices using triphenylphosphine oxide (Ph3PO) layers. The devices with a Ph3PO layer show high current density at a low voltage. For example, the current density of 20mA∕cm2 is achieved at a low voltage of 2.9V for the device consisted of 4,4′,4″-tris[N-(2-naphthyl)-N-phenyl-amino]-triphenylamine (2-TNATA), 4,4′-bis(2,2′-diphenylvinyl)-1,1′-biphenyl (DPVBi), and Ph3PO layers. Due to the good electron conduction property of Ph3PO, a luminance of 1017cd∕m2 is achieved at a low voltage of 3.0V in a device with a structure of ITO/2-TNATA/DPVBi:rubrene (1%,10nm)∕DPVBi (30nm)∕Ph3PO (60nm)∕LiF∕Al.

Efficient white organic light-emitting diodes based on iridium complex sensitized copper complex

Efficient double emission-layer white organic light-emitting diodes comprising a yellow emission from bis[(4,6-difluorophenyl)-pyridinato-N,C2](picolinato)Ir(III) (FIrpic) sensitized [Cu(bis[2-(diphenylphosphino)phenyl]ether) (6,7-Dicyanodipyrido[2,2-d : 2′, 3′-f] quinoxaline)]BF4(CuI complex) and a blue emission from 4, 4′-bis(2,2′-diphenylvinyl)-1, 1′-biphenyl (DPVBi) were demonstrated. The emission spectrum can be fine tuned by effectively controlling the thicknesses of the two emission layers. The optimized device with 18 nm FIrpic and the CuI complex codoped 4, 4′-N,N′-dicarbazole-biphenyl layer and 12 nm DPVBi layer shows a maximum current efficiency of 8.5 cd A−1, a maximum power efficiency of 5.3 lm W−1 and a maximum luminance of 3290 cd m−2. Moreover, the device exhibits a CIE coordinate of (0.345, 0.357) at a bias of 8 V and a slight colour variation with increased voltage from 6 to 16 V.

Dual Partial Dye Doping for Chromaticity Tuning and Performance Enhancement of White OLEDs

In general, a guest dopant is doped into a single host matrix for white-light emission with two complementary colors. In this work, however, we have fabricated a white organic light-emitting diode (WOLED) based on dual partial dye doping in which a guest dopant is partially doped into two different host emitters; namely, orange-red emitting 4-(dicyanomethylene)-2-methyl-6-(p-dimethylaminos-tyryl)-4H-pyran (DCM) is partially doped into both blue-emitting 4, 4'-bis(2,2'-diphenylvinyl)-1,1'-biphenyl (DPVBi) and green-emitting Tris-(8-hydroxyquinoline) aluminum (Alq3). We demonstrate that dual partial dye doping allows us to finely tune the Commission Internationale d'Eclairage (CIE) chromaticity coordinates to the equienergy white point (x = 0.33, y = 0.33). In addition, it enhances device performance further, compared to WOLEDs based on DCM partially doped into a single host matrix (either DPVBi or Alq3). Moreover, the dual partial doping scheme is shown to provide a way of suppressing the self-quenching effect (singlet-singlet annihilation). For a systematic study, we have implemented a comprehensive numerical model and performed simulations of the OLED structure, providing a clear understanding with regard to the underlying physics of OLEDs. We also carry out an investigation of the effects of key design parameters such as the doped layer position and thickness and dye.

Doped and non-doped organic light-emitting diodes based on a yellow carbazole emitter into a blue-emitting matrix

A new carbazole derivative with a 3,3′-bicarbazyl core 6,6′-substituted by dicyanovinylene groups (6,6′-bis(1-(2,2′-dicyano)vinyl)- N, N′-dioctyl-3,3′-bicarbazyl; named (OcCz2CN) 2, was synthesized by carbonyl-methylene Knovenagel condensation, characterized and used as a component of multilayer organic light-emitting diodes (OLEDs). Due to its π-donor–acceptor type structure, (OcCz2CN) 2 was found to emit a yellow light at λ max = 590 nm (with the CIE coordinates x = 0.51; y = 0.47) and was used either as a dopant or as an ultrathin layer in a blue-emitting matrix of 4,4′-bis(2,2′-diphenylvinyl)-1,1′-biphenyl (DPVBi). DPVBi (OcCz2CN) 2-doped structure exhibited, at doping ratio of 1.4 weight %, a yellowish–green light with the CIE coordinates ( x = 0.31; y = 0.51), an electroluminescence efficiency η EL = 1.3 cd/A, an external quantum efficiency η ext = 0.4 % and a luminance L = 127 cd/m 2 (at 10 mA/cm 2) whereas for non-doped devices utilizing the carbazolic fluorophore as a thin neat layer, a warm white with CIE coordinates ( x = 0.40; y = 0.43), η EL = 2.0 cd/A, η ext = 0.7%, L = 197 cd/m 2 (at 10 mA/cm 2) and a color rendering index (CRI) of 74, were obtained. Electroluminescence performances of both the doped and non-doped devices were compared with those obtained with 5,6,11,12-tetraphenylnaphtacene (rubrene) taken as a reference of highly efficient yellow emitter.

White Organic Light-Emitting Diodes Based on Three Emissive Layers

We report white organic light-emitting diodes (WOLEDs) based on 4,4′-bis(2,2′-diphenyl vinyl)- 1,1′-biphenyl (DPVBi), fac tris(2-phenylpyridine)iridium (Ir(ppy)3) and bis(2-(2′-benzo[4,5-a]thienyl) pyridinato-N,C3′) iridium (acetylacetonate) (Btp2Ir(acac)). White OLEDs with the structure of ITO/NPB/DPVBi/CBP: Ir(ppy)3/BCP: Btp2Ir(acac)/Alq3/Liq/Al were fabricated and characterized, where Ir(ppy)3 and Btp2Ir(acac) were used as a green phosphorescent dye and red phosphorescent dye, respectively. And DPVBi was used as blue emitting layer. The electroluminescent spectra of the device consisted of blue fluorescent, green phosphorescent and red phosphorescent emissions. The optimized device exhibited white light emission between 10 and 15 V. A maximum luminance of 11000 cd/m2 with CIE coordinates of (0.322, 0.344) was reached at 15 V. The white light emission is related to the simultaneous exciton formation on both sides of the CBP/BCP interface. The main exciton formation zone gradually shifts to the CBP side from the BCP side with increase of voltage in the devices. As a result, the intensity of the green and blue emission increased gradually relative to the red emission with increasing voltage.

Efficiency Enhancement Mechanism of Organic Light-Emitting Devices with an Alq3 Emitting Layer Containing a DPVBi Wide Bandgap Doping Agent

The efficiency of the organic light-emitting devices (OLEDs) with a tris-(8-hydroxyquinoline) aluminum (Alq3) emitting layer (EML) containing a 4,4-bis(2,2diphenyl vinyl)-1,1-biphenyl (DPVBi) doping agent was significantly enhanced in comparison to that with an Alq3 EML without a DPVBi doping agent. The enhancement of the injection efficiency of the OLEDs with an EML doped with a wide-bandgap doping agent was attributed to a decrease in the trap charge density existing in the EML resulting from the existence of the DPVBi doping agent. The luminescence mechanism of the OLEDs fabricated utilizing an Alq3 EML containing a DPVBi wide-bandgap doping agent is described on the basis of the experimental results.

White organic light-emitting diodes with fine chromaticity tuning via ultrathin layer position shifting

Nondoped white organic light-emitting diodes using an ultrathin yellow-emitting layer of rubrene (5,6,11,12-tetraphenylnaphtacene) inserted on either side of the interface between a hole-transporting 4,4′-bis[N-(1-naphtyl)-N-phenylamino]biphenyl (α-NPB) layer and a blue-emitting 4,4′-bis(2,2′-diphenylvinyl)-1,1′-biphenyl (DPVBi) layer are described. Both the thickness and the position of the rubrene layer allow fine chromaticity tuning from deep blue to pure yellow via bright white with CIE coordinates (x=0.33, y=0.32), an ηext of 1.9%, and a color rendering index of 70. Such a structure also provides an accurate sensing tool to measure the exciton diffusion length in both DPVBi and NPB (8.7 and 4.9nm, respectively).

White organic light-emitting devices with non-doped-type structure

A non-doped-type structure was proposed for obtaining organic light-emitting devices with high-efficiency and full-spectrum white light emission. The device structure included indium tin oxide glass substrate/450 Å 4,4′,4″-tris{ N-(3-methylphenyl)- N-phenylamin}triphenylamine (m-MTDATA) hole injection layer/100 Å N, N′-bis-(1-naphthyl)- N, N′-diphenyl-1,1′-biph-enyl-4,4′-diamine (NPB) hole transport layer/150 Å 4,4′-bis(2,2′-diphenylvinyl)-1,1′-biphenyl (DPVBi) blue emitting layer/ultrathin [2-methyl-6-[2-(2,3,6,7-tetrahydro-1H, 5H-benzo[ij] quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene] propane-dinitrile (DCM2) yellow-emitting layer/ 80 Å 4,7-diphenyl-1,10-phenanthroline (BPhen) electron transporting layer and hole blocking layer/600 Å tris (8-hydroxyquinoline) aluminium (Alq3) electron-transporting layer /10 Å lithium fluoride (LiF)/aluminum (Al). A white emission (Commission Internationale de l’Eclairage 1931 chromaticity coordinate) ( X = 0.3556, Y = 0.3117) at 5 V and ( X = 0.282, Y = 0.2658) at 15 V was obtained. Its luminance was 11,497 cd/m 2 at 15 V, and the maximum efficiency was 4.8 lm/W at 5 V.

Highly efficient multilayer organic pure blue light emitting diodes with substituted carbazoles compounds in the emitting layer

Bright blue organic light-emitting diodes (OLEDs) based on 1, 4, 5, 8, N-pentamethylcarbazole (PMC) and on dimer of N-ethylcarbazole (N, N′-diethyl-3, 3′-bicarbazyl) (DEC) as emitting layers or as dopants in a 4, 4′-bis(2, 2′-diphenylvinyl)-1, 1′-biphenyl (DPVBi) matrix are described. Pure blue light with the CIE coordinates (x = 0.153, y = 0.100), electroluminescence efficiency ηEL of 0.4 cd A−1, external quantum efficiency ηext of 0.6% and luminance L of 236 cd m−2 (at 60 mA cm−2) were obtained with PMC as an emitter and the 2, 9-dimethyl-4, 7-diphenyl-1, 10-phenantroline (BCP) as a hole-blocking material in five-layer emitting devices. The highest efficiencies ηEL of 4.7 cd A−1 and ηext = 3.3% were obtained with a four-layer structure and a DPVBi DEC-doped active layer (CIE coordinates x = 0.158, y = 0.169, λpeak = 456 nm). The ηext value is one the highest reported at this wavelength for blue OLEDs and is related to an internal quantum efficiency up to 20%.