New spiro[benzotetraphene-fluorene] Derivatives: Synthesis and Application in Sky-Blue Fluorescent Host Materials

Blue light-emitting spiro[benzotetraphene-fluorene] (SBTF)-based host materials, 3-(1-naphthyl)-10-naphthylspiro[benzo[ij]tetraphene-7,9′-fluorene] (1), 3-(2-naphthyl)-10-naphthylspiro[benzo[ij]tetraphene-7,9′-fluorene] (2), and 3-[2-(6-phenyl)naphthyl]-10-naphthylspiro[benzo[ij]tetraphene-7,9′-fluorene] (3) were designed and prepared via multi-step Suzuki coupling reactions. Introducing various aromatic groups into SBTF core lead to a reduction in band gap and a determination of the color purity and luminescence efficiency. Typical sky-blue fluorescent organic light emitting diodes with the configuration of ITO/N,N′-di(1-naphthyl)-N,N′-bis[(4-diphenylamino)phenyl]-biphenyl-4,4′-diamie (60 nm)/N,N,N′,N′-tetra(1-biphenyl)-biphenyl-4,4′-diamine (30 nm)/host: dopant (30 nm, 5 %)/LG201 (electron transporting layer, 20 nm)/LiF/Al were developed using SBTF derivatives as a host material and p-bis(p-N,N-diphenyl-aminostyryl)benzene (DSA-Ph) as a sky-blue dopant material. A device obtained from three materials doped with DSA-Ph showed color purity of 0.148 and 0.239, a luminance efficiency of 7.91 cd/A, and an external quantum efficiency >4.75 % at 5 V.     

Efficient white polymer light-emitting diodes based on a phosphorescent iridium complex and a fluorescent silole and carbazole copolymer

White polymer light-emitting diodes (WPLEDs) were fabricated with blue phosphorescent iridium bis(2-(4,6-difluorophenyl)-pyridinato-N,C²′) picolinate (FIrpic) and red fluorescent silole and carbazole copolymer PCz-MPTST within a poly(N-vinylcarbazole) (PVK): 1,3-bis[(4-tert-butylphenyl)-1,3,4- oxadiazolyl] phenylene (OXD-7) host matrix. Efficient white emission consisting two emission peaks was achieved with luminous efficiency of 9.2 cd/A and CIE coordinates of (0.37, 0.40). By means of transient photoluminescence response, energy transfer among the blending components was investigated and discussed.     

基于7-（9H-carbazol-9-yl）-N,N-diphenyl-9, 9’-spirobi[fluoren]-2-amine主体材料的高效红色电致磷光器件

研究了基于新型骨架7-（9H-carbazol-9-yl）-N,N-diphenyl-9,9’-spirobi[fluoren]-2-amine（CzFA）双极性主体材料的红色电致磷光器件的光电特性。研究结果表明：将红色磷光染料iridium（Ⅲ）bis[2-methyldibenzo-（f,h）quinoxaline]（acetylacetonate）（Ir（MDQ）₂（acac））掺杂到CzFA主体材料中,以其制备的电致发光器件具有优良的特性,最大电流效率为27.8 cd/A,最大功率效率为21.8 lm/W,最大功率效率几乎是先前报道的主体材料为CBP器件（13.7 lm/W）的1.6倍。这种咔唑-螺二芴-二胺基团所组成的双极性主体材料对于提升磷光器件的性能起到了重要的作用。     

Synthesis,photophysical and electro-optical properties of bis-carbazolyl methane based host material for pure-blue phosphorescent OLED

A new high triplet-energy host material, 9-(4-(bis(9-ethyl-9H-carbazol-3-yl)methyl)phenyl)-9H-carbazole (bis-CMPC), was synthesized and its device performance of phosphorescent organic light-emitting diode was investigated. This host material showed a high triplet energy (～2.95 eV) and good thermal stability. Highly efficient pure-blue PHOLED was obtained when employing bis-CMPC as the host material and bis((3,5-difluoro-4-cyanophenyl)pyridine) iridium picolinate as the guest material. The maximum external quantum efficiency of the device reached as high as 13.3% with a pure-blue color coordinate of (0.14, 0.21).     

An ethylcarbazole based phosphine oxide derivative as a host for deep blue phosphorescent organic light-emitting diode

Deep blue phosphorescent organic light-emitting diodes (PHOLEDs) were developed using a 9-ethylcarbazole based phosphine oxide material (EPO1). A high triplet energy of 3.01 eV was obtained from the EPO1 host material and efficient energy transfer from the host to the deep blue emitting phosphorescent dopant was observed. A high quantum efficiency of 7.9% with a color coordinate of (0.15, 0.17) was achieved in the deep blue PHOLED using the EPO1 host material.     

Synthesis and electroluminescent properties of a carbozole-functionalized europium(III) complex

A novel europium(III) complex, tris(dibenzoylmethanate){1-[9-hexyl-9H-carbazole]-2-(2-pyridyl)-benzimidazole}europium(III) [Eu(DBM)₃(CAR-PyBM)] functionalized by a carbozole fragment, was synthesized and used as emitting material in organic electroluminescent (EL) devices. Compared with the device based on an unfunctional Eu(III) complex, [Eu(DBM)₃HPyBM] (HPyBM=2-(2-pyridyl)benzimidazole), the EL performances of the device using [Eu(DBM)₃(CAR-PyBM)] as an emitter was significantly enhanced due to the improvement of hole-transporting ability. The maximum efficiency and luminance of red emission achieved from the device with the configuration of ITO/N,N′-diphenyl-N,N′-bis(3-methylphenyl)-1,1′-biphenyl-4,4′diamine (TPD, 50 nm)/ [Eu(DBM)₃(CAR-PyBM)] (30 nm)/1,3,5-tirs-(N-phenylbenzimidazol-2-yl)benzene (TPBI, 20 nm)/LiF (1.5 nm)/Al were 4.2 cd/A and 200 cd/m², respectively.     

2,5-di(thiophen-2-yl)thiazolo[5,4-d]thiazole-based donor-acceptor type copolymers for photovoltaic cells

Alternating donor-acceptor type copolymers, poly[{5,11-di(9′-heptadecanyl)indolo[3,2-b]carbazole}-alt-{2,5-di(thiophen-2-yl)thiazolo[5,4-d]thiazole-5,5′-diyl}] (PIC-TZ) and poly[{6,6′,12,12′-tetraoctylindeno[1,2-b]fluorene}-alt-{2,5-di(thiophen-2-yl)thiazolo[5,4-d]thiazole-5,5′-diyl}] (PIF-TZ), were synthesized and examined for applications in polymeric photovoltaic cells. The polymers have a fused coplanar main backbone with good planarity for intermolecular packing and high charge mobility. The indolocarbazole and indenofluorene units contain two or four binding sites for alkyl substituents that have pronounced solution processiblity compared to the carbazole and fluorene moieties. The number-average molecular weights (M_n) of the synthesized polymers were determined to be 11,000 g/mol (PDI = 2.27) for PIC-TZ, and 17,000 g/mol (PDI = 1.77) for PIF-TZ. The optical band gap of PIC-TZ and PIF-TZ in film was determined to be 2.14 eV and 2.21 eV, respectively, and an electrochemical study confirmed the desirable HOMO/LUMO levels of the copolymers, which enabled efficient electron transfer and a high open circuit voltage (V_OC) when blending them with fullerene derivatives. The space charge limited current mobility measurements showed a hole mobility of 10⁻³ cm² V⁻¹ s⁻¹ for the copolymers. When the polymers were blended with [6,6]phenyl-C₆₁-butyric acid methyl ester (PCBM), PIC-TZ showed the best performance with V_OC, short-circuit current and power conversion efficiency of 0.86 V, 4.16 mA/cm² and 1.64%, respectively, under AM 1.5G illumination conditions (100 mW cm⁻²).     

Photoluminescence and electroluminescence of a novel green-yellow emitting material-5,6-Bis-[4-(naphthalene-1-yl-phenyl-amino)-phenyl]-pyrazine-2,3-dicarbonitrile

A new compound with intramolecular charge transfer (ICT) property—5,6-Bis-[4-(naphthalene-1-yl-phenyl-amino)-phenyl]-pyrazine-2,3-dicarbonitrile(BNPPDC) was synthesized. The new compound was strongly fluorescent in non-polar and moderately polar solvents, as well as in thin solid film. The absorption and emission maxima shifted to longer wavelength with increasing solvent polarity. The fluorescence quantum yield also increased with increasing solvent polarity from non-polar to moderately polar solvents, then decreased with further increase of solvent polarity. This indicates both “positive” and “negative” solvatokinetic effects co-existed. Using this material as hole-transporting emitter and host emitter, we fabricated two electroluminescent (EL) devices with structures of A (ITO/BNPPDC (45 nm)/1,3,5-tris(N-phenylbenzimidazol-2-yl)benzene (TPBI) (45 nm)/Mg:Ag (200 nm) and B (ITO/N,N′-diphenyl-N,N′-bis-(3-methylphenyl) (1,1′-diphenyl)4,4′-diamine (TPD) (50 nm)/BNPPDC (20 nm)/1,3,5-tris(N-phenylbenzimidazol-2-yl)benzene (TPBI) (45 nm)/Mg:Ag (200 nm). The devices showed green-yellow EL emission with good efficiency and high brightness. For example, the device A exhibited a high brightness of 17400 cd/m² at a driving voltage of 11 V and a very low turn-on voltage (2.9 V), as well as a maximum luminous efficiency 3.61 cd/A. The device B showed a similar performance with a high brightness of 12650 cd/m² at a driving voltage of 13 V and a maximum luminous efficiency 3.62 cd/A. In addition, the EL devices using BNPPDC as a host and 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) as a dopant (configuration: ITO/TPD (60 nm)/BNPPDC:DCJTB (2%) (30 nm)/TPBI (35 nm)/Mg:Ag (200 nm)) showed a good performance with a brightness of 150 cd/m² at 4.5 V, a maximum brightness of 12600 cd/m² at 11.5 V, and a maximum luminous efficiency of 3.30 cd/A.     

Red organic light-emitting diodes with high efficiency,low driving voltage and saturated red color realized via two step energy transfer based on ADN and Alq3 co-host system

We demonstrated efficient red organic light-emitting diodes based on a wide band gap material 9,10-bis(2-naphthyl)anthracene (ADN) doped with 4-(dicyano-methylene)-2-t-butyle-6-(1,1,7,7-tetramethyl-julolidyl-9-enyl)-4H-pyran (DCJTB) as a red dopant and 2,3,6,7-tetrahydro-1,1,7,7,-tetramethyl-1H,5H,11H-10(2-benzothiazolyl)quinolizine-[9,9a,1gh]coumarin (C545T) as an assistant dopant. The typical device structure was glass substrate/ITO/4,4′,4″-tris(N-3-methylphenyl-N-phenyl-amino)triphenylamine (m-MTDATA)/N,N′-bis(naphthalene-1-yl)-N,N′-diphenyl-benzidine (NPB)/[ADN:Alq₃]:DCJTB:C545T/Alq₃/LiF/Al. It was found that C545T dopant did not by itself emit but did assist the energy transfer from the host (ADN) to the red emitting dopant via cascade energy transfer mechanism. The OLEDs realized by this approach significantly improved the EL efficiency. We achieved a significant improvement regarding saturated red color when a polar co-host emitter (Alq₃) was incorporated in the matrix of [ADN:Alq₃]. Since ADN possesses a considerable high electron mobility of 3.1 × 10⁻⁴ cm²  V⁻¹ s⁻¹, co-host devices with high concentration of ADN (>70%) exhibited low driving voltage and high current efficiency as compared to the devices without ADN. We obtained a device with a current efficiency of 3.6 cd/A, Commission International d’Eclairage coordinates of [0.618, 0.373] and peak λ_max = 620 nm at a current density of 20 mA/cm². This is a promising way of utilizing wide band gap material as the host to make red OLEDs, which will be useful in improving the electroluminescent performance of devices and simplifying the process of fabricating full color OLEDs.     

亚单层黄色有机发光器件制备与光电性能研究

采用掺杂薄层作为亚单层有机发光技术,利用沉积在有机发光器件发光层中的亚单层分子[2-methyl-6-[2-(2,3,6,7-tetrahydro-1H,5H-benzo[ij] quinolizin-9-yl) ethenyl]-4H-pyran-4-ylidene] propane-dinitrile （DCM2）作为探针,同时改变DCM2层的位置,制备了四种亚单层结构的有机发光器件,对有机发光器件中激子的形成与扩散进行了研究,通过对各器件不同条件下的电致发光谱、发光强度和发光效率的对比研究,得到在N,N′-bis-(1-naphthyl)-N,N′-diphenyl-1,1′-biph-enyl-4,4′-diamine（NPB）/(8-hydroxyquinoline) aluminium（Alq）异质结界面处引入亚单层DCM2可以使DCM2分子获得的激子数量最多,获得了高效率的黄色有机发光器件.从其中总结规律,对有机发光器件制作有一定的指导作用.     

Solution-processed white organic light-emitting devices based on small-molecule materials

We investigated solution-processed films of 4,4′-bis(2,2-diphenylvinyl)-1,1′-bibenyl (DPVBi) and its blends with N,N′-bis(3-methylphenyl)-(1,1′-biphenyl)-4,4′-diamine (TPD) by atomic force microscopy (AFM). The AFM result shows that the solution-processed films are pin-free and their morphology is smooth enough to be used in OLEDs. We have developed a solution-processed white organic light-emitting device (WOLEDs) based on small-molecules, in which the light-emitting layer (EML) was formed by spin-coating the solution of small-molecules on top of the solution-processed hole-transporting layer. This WOLEDs, in which the EML consists of co-host (DPVBi and TPD), the blue dopant (4,4′-bis[2-(4-(N,N-diphenylamino)phenyl)vinyl]biphenyl) and the yellow dye (5,6,11,12-tetraphenylnaphtacene), has a current efficiency of 6.0 cd/A at a practical luminance of 1000 cd/m², a maximum luminance of 22500 cd/m², and its color coordinates are quite stable. Our research shows a possible approach to achieve efficient and low-cost small-molecule-based WOLEDs, which avoids the complexities of the co-evaporation process of multiple dopants and host materials in vacuum depositions.     

A luminescent dinuclear Eu(III) complex based on 2,8-bis(4′,4′,4′,-trifluoro-1′,3′-dioxobutyl)-dibenzothiophene for light-emitting diodes

A dinuclear Eu (III) complex Eu₂(dbt)₃·4H₂O was synthesized, where H₂dbt was 2,8-bis(4′,4′,4′,-trifluoro-1′,3′-dioxobutyl)-dibenzothiophene. The complex emits the characteristic red luminescence of Eu³⁺ ion due to the ⁵D₀→⁷F_J(J=0-4) transitions under 395 nm-light excitation with a luminescent quantum efficiency of 17%. The complex is thermally stable up to 280 °C. It was found that the complex can be effectively excited by a 395 nm-emitting InGaN chip. Bright red light was obtained using the complex as light color-conversion material.     

High-performance organic red-light-emitting device based on DCJTB and a new host material

An efficient red-light-emitting device using a new host material (DPF) and a red dopant (DCJTB) with a configuration of ITO/NPB (50 nm)/DCJTB:DPF (2%, 10 nm)/TPBI (30 nm)/LiF (0.5 nm)/Mg:Ag has been fabricated and investigated. The red OLED yields a brightness of 9270 cd/m² at 10 V, a maximum current efficiency of 4.2 cd/A and a maximum power efficiency of 3.9 lm/W. Using DPF as host material, the performance is much better than that of a prototypical Alq₃-based device, which has a maximum efficiency of 1.9 cd/A and 0.6 lm/W. The performance is even comparable with red OLEDs using an assist dopant or a cohost emitter system. Results of this work indicate that DPF is a promising host material for red OLEDs with high efficiency and simple device structure.     

A solution-processable small-organic molecules containing carbazole or phenoxazine structure as hole-transport materials for perovskite solar cells

Three low molecular weight compounds bearing carbazole units (1,6-di{3-[2-(4-methylphenyl)vinyl]carbazol-9-yl}hexane and 9,9'-di{6-[3-(2-(4-methylphenyl)vinyl)-9-carbazol-9-yl]hexyl}-[3,3']bicarbazole) and phenoxazine structure (10-butyl-3,7-diphenylphenoxazine) were tested as hole-transporting materials in perovskite solar cells. Two of them were successfully applied as hole transporting layers in electroluminescent light emitted diodes. The examined compounds were high-thermally stable with decomposition temperature found at the range of 280–419 °C. Additionally, DSC measurement revealed that they can be converted into amorphous materials. The compounds possess adequate ionization potentials, to perovskite energy levels, being in the range of 5.15–5.36 eV. The significant increase in power conversion efficiency from 1.60% in the case of a device without hole-transporting layer, to 5.31% for device with 1,6-di{3-[2-(4-methylphenyl)vinyl]carbazol-9- yl}hexane was observed.     

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 red light phosphorescence emission in simple bi-layered structure organic devices with fluorescent host-phosphorescent guest system

Highly efficient red phosphorescent devices comprising a simple bi-layered structure using tris(1-phenylisoquinoline)iridium (Ir(piq)₃) doped in a narrow band-gap fluorescent host material, bis(10-hydroxybenzo [h] quinolinato)beryllium complex (Bebq₂) are reported. The driving voltage to reach 1000 cd/m² is 3.5 V in Bebq₂:Ir(piq)₃ red phosphorescent device. With a dopant concentration of as low as 4%, the current and power efficiency values of 8.41 cd/A and 7.34 lm/W are obtained in this PHOLEDs, respectively. External quantum efficiency (EQE) of 14.5% is noticed in this red phosphorescent device, promising to high brightness applications.     

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/m² 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.     

Enhancement of electroluminescent properties of organic optoelectronic integrated device by doping phosphorescent dye

Organic optoelectronic integrated devices(OIDs) with ultraviolet(UV) photodetectivity and different color emitting were constructed by using a thermally activated delayed fluorescence(TADF) material 4, 5-bis(carbazol-9-yl)-1, 2-dicyanobenzene(2 CzPN) as host. The OIDs doping with typical red phosphorescent dye [tris(1-phenylisoquinoline)iridium(Ⅲ), Ir(piq)_3], orange phosphorescent dye {bis[2-(4-tertbutylphenyl)benzothiazolato-N,C~(2')]iridium(acetylacetonate),(tbt)_2 Ir(acac)}, and blue phosphorescent dye [bis(2, 4-di-fluorophenylpyridinato)-tetrakis(1-pyrazolyl)borate iridium(Ⅲ), FIr6] were investigated and compared. The(tbt)_2 Ir(acac)-doped orange device showed better performance than those of red and blue devices, which was ascribed to more effective energy transfer. Meanwhile, at a low dopant concentration of 3 wt.%, the(tbt)_2 Ir(acac)-doped OIDs showed the maximum luminance, current efficiency, power efficiency of 70786 cd/m~2, 39.55 cd/A, and 23.92 lm/W, respectively, and a decent detectivity of 1.07 × 10~(11) Jones at a bias of -2 V under the UV-350 nm illumination. This work may arouse widespread interest in constructing high efficiency and luminance OIDs based on doping phosphorescent dye.     

Synthesis and electroluminescence properties of benzothiazole derivatives

Benzothiazole-based blue fluorescent materials N-(4-(benzo[d]thiazol-2-yl)phenyl)-N-phenylbenzenamine (BPPA) and N-(4-(benzo[d]thiazol-2-yl)phenyl)-N-phenylnaphthalen-1-amine (BPNA) were synthesized for use in organic light-emitting diodes (OLEDs). Electroluminescent device with a configuration of ITO/NPB/BPPA/BCP/Alq₃/LiF/Al showed a maximum brightness of 3760 cd/m² at 14.4 V with the CIE coordinates of (0.16, 0.16). A current efficiency of 3.01 cd/A and an external quantum efficiency of 2.37% at 20 mA/cm² were obtained from this device. Molecules derived from BPPA and BPNA with incorporated dicyanomethylidene, which is a functional group for most red fluorescent molecules, were designed, synthesized and characterized to study the red fluorescence properties of the benzothiazole derivatives.     

Influence of interface modification on the performance of polymer/Bi2S3 nanorods bulk heterojunction solar cells

In this paper, bulk heterojunction photovoltaic devices based on the poly[2-methoxy-5-(3′,7′-dimethyloctyloxy)-1,4-phenylenevinylene] (MDMO-PPV):Bi₂S₃ nanorods hybrid material were present. To optimize the performance of the devices, the interface modification of the hybrid material that has a significant impact on the exciton dissociation efficiency was studied. An improvement in the device performance was achieved by modifying the Bi₂S₃ surface with a thin dye layer. Moreover, modifying the Bi₂S₃ surface with anthracene-9-carboxylic acid can enhance the performance further. Compared with the solar cells with Bi₂S₃ nanorods hybrid with the MDMO-PPV as the active layer, the anthracene-9-carboxylic acid modified devices are better in performance, with the power conversion efficiency higher by about one order in magnitude.