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1.
    
Three new starburst DCM (4‐(dicyanomethylene)‐2‐methyl‐6‐[4‐(dimethylaminostyryl)‐4H‐pyran]) derivatives, 4,4′,4′′‐tris[2‐(4‐dicyanomethylene‐6‐t‐butyl‐4H‐pyran‐2‐yl)‐ethylene]triphenylamine (TDCM), 4,4′,′′‐tris[2‐(4‐(1′,3′‐indandione)‐6‐t‐butyl‐4H‐pyran‐2‐yl)‐ethylene]triphenylamine (TIN), and 4‐methoxy‐4′,4′′‐bis[2‐(4‐(1′,3′‐indandione)‐6‐t‐butyl‐4H‐pyran‐2‐yl)‐ethylene]triphenylamine (MBIN), have been designed and synthesized for application as red‐light emitters in organic light‐emitting diodes (OLEDs). Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) reveal their extremely high glass‐transition temperatures and decomposition temperatures, as well as their low tendency to crystallize. Photoluminescence and electroluminescence measurements show that they exhibit a greatly restricted concentration‐quenching effect compared to DCM1 (4‐(dicyanomethylene)‐2‐methyl‐6‐[p‐(N,N‐dimethylamino)‐styryl]‐4H‐pyran), a simple but typical DCM‐type dye, as a result of their non‐planar, three‐dimensional structures that result from their unique propeller‐like triphenylamine electron‐donating cores. The peripheral electron‐withdrawing moieties also play a key role in the restriction of concentration quenching. That is, TIN and MBIN, bearing 1,3‐indandione acceptors, emit more efficiently than TDCM and DCM1, which have dicyanomethylene as acceptors at a high doping concentration of 10 wt.‐% in poly(9‐vinylcarbazole) (PVK) film, irrespective of whether they are photoexcited or electroexcited, though their fluorescence quantum yields in dilute solutions are much lower than that of DCM1. By way of the co‐doping approach, the electroluminescence device with the configuration indium tin oxide (ITO)/PVK:MBIN(10 wt.‐%):tris(4‐(2‐phenylethynyl)‐phenyl)amine (TPA; 30 wt.‐%) (70 nm)/2,9‐dimethyl‐4,7‐diphenyl‐1,10‐phenanthroline (BCP; 20 nm)/tris(8‐quinolinolato) aluminum (Alq3;15 nm)/LiF (0.3 nm)/Al (150 nm) exhibits a turn‐on voltage of 5.1 V, a maximum luminance of 6971 cd m–2, a maximum efficiency of 6.14 cd A–1 (405 cd m–2), and chromaticity coordinates of (0.66,0.33). The encouraging electroluminescence performance suggests potential applications of the starburst DCM red‐light emitters in OLEDs.  相似文献   

2.
We report the synthesis, photophysics and electrochemical properties of naphthalene–benzofuran compound 1 and its application in organic light emitting devices. Fluorescent deep-blue emitting devices employing 1 as the emitting dopant embedded in 4-4′-bis(9-carbazolyl)-2,2′-biphenyl (CBP) host show the peak external quantum efficiency of 4.5% and Commission Internationale d’Énclairage (CIE) coordinates of (0.15, 0.07). Hybrid white devices using fluorescent blue emitting layer with 1 and a phosphorescent orange emitting layer based on an iridium-complex show the peak external quantum efficiency above 10% and CIE coordinates of (0.31, 0.37).  相似文献   

3.
    
Two compounds, 2,3‐dicyano‐5,6‐di(4′‐diphenylamino‐biphenyl‐4‐yl)pyrazine (CAPP) and 6,7‐dicyano‐2,3‐di(4′‐diphenylamino‐biphenyl‐4‐yl)quinoxaline (CAPQ), capable of intramolecular charge transfer, have been designed and synthesized in high yield by a convenient procedure. The compounds have been fully characterized spectroscopically. They have a high thermal stability and show bright light emission both in non‐polar solvents and in the solid state. Moreover, they exhibit excellent reversible oxidation and reduction waves. The higher energy level of the highest occupied molecular orbital (–5.3 eV) and the triphenylamine group are advantageous for hole‐injection/transport. In addition, the high electron affinities of 3.4 eV and the observed reversible reductive process suggest that these compounds enhance electron injection and have potential for use in electron transport. Three types of non‐doped red‐light‐emitting diodes have been studied using CAPP and CAPQ as the electron‐transporting and host‐light‐emitting layers, respectively. The devices exhibit red electroluminescence (EL), and constant Commission Internationale de l'Eclairage coordinates have been observed on increasing the current density. Pure red EL of CAPP, with a maximum brightness of 536 cd m–2 and an external quantum efficiency of 0.7 % in ambient air, was achieved.  相似文献   

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5.
    
Two novel naphtho[1,2‐d]imidazole derivatives are developed as deep‐blue, light‐emitting materials for organic light‐emitting diodes (OLEDs). The 1H‐naphtho[1,2‐d]imidazole based compounds exhibit a significantly superior performance than the 3H‐naphtho[1,2‐d]imidazole analogues in the single‐layer devices. This is because they have a much higher capacity for direct electron‐injection from the cathode compared to their isomeric counterparts resulting in a ground‐breaking EQE (external quantum efficiency) of 4.37% and a low turn‐on voltage of 2.7 V, and this is hitherto the best performance for a non‐doped single‐layer fluorescent OLED. Multi‐layer devices consisting of both hole‐ and electron‐transporting layers, result in identically excellent performances with EQE values of 4.12–6.08% and deep‐blue light emission (Commission Internationale de l'Eclairage (CIE) y values of 0.077–0.115) is obtained for both isomers due to the improved carrier injection and confinement within the emissive layer. In addition, they showed a significantly better blue‐color purity than analogous molecules based on benzimidazole or phenanthro[9,10‐d]imidazole segments.  相似文献   

6.
    
Solid‐state lighting (SSL) is one of the biggest achievements of the 20th century. It has completely changed our modern life with respect to general illumination (light‐emitting diodes), flat devices and displays (organic light‐emitting diodes), and small labeling systems (light‐emitting electrochemical cells). Nowadays, it is however mandatory to make a transition toward green, sustainable, and equally performing lighting systems. In this regard, several groups have realized that the actual SSL technologies can easily and efficiently be improved by getting inspiration from how natural systems that manipulate light have been optimized over millennia. In addition, various natural and biocompatible materials with suitable properties for lighting applications have been used to replace expensive and unsustainable components of current lighting devices. Finally, SSL has also started to revolutionize the biomedical field with the achievement of efficient implantable lighting systems. Herein, the‐state‐of‐art of (i) biological materials for lighting devices, (ii) bioinspired concepts for device designs, and (iii) implantable SSL technologies is summarized, highlighting the perspectives of these emerging fields.  相似文献   

7.
    
A new series of highly efficient red‐emitting phosphorescent Ir(III) complexes, (Et‐CVz‐PhQ)2Ir(pic‐N‐O), (Et‐CVz‐PhQ)2Ir(pic), (Et‐CVz‐PhQ)2Ir(acac), (EO‐CVz‐PhQ)2Ir(pic‐N‐O), (EO‐CVz‐PhQ)2Ir(pic), and (EO‐CVz‐PhQ)2Ir(acac), based on carbazole (CVz)‐phenylquinoline (PhQ) main ligands and picolinic acid N‐oxide (pic‐N‐O), picolinic acid (pic), and acetylacetone (acac) ancillary ligands, are synthesized for phosphorescent organic light‐emitting diodes (PhOLEDs), and their photophysical, electrochemical, and electroluminescent (EL) properties are investigated. All of the Ir(III) complexes have high thermal stability and emit an intense red light with an excellent color purity at CIE coordinates of (0.65,0.34). Remarkably, high‐performance solution‐processable PhOLEDs were fabricated using Ir(III) complexes with a pic‐N‐O ancillary ligand with a maximum external quantum efficiency (5.53%) and luminance efficiency (8.89 cd A?1). The novel use of pic‐N‐O ancillary ligand in the synthesis of phosphorescent materials is reported. The performance of PhOLEDs using these Ir(III) complexes correlates well with the results of density functional theory calculations.  相似文献   

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9.
    
Lead halide perovskite, as an emerging semiconductor, provides a fire‐new opportunity for high‐definition display and solid‐state lighting. Earthshaking improvements are implemented in green, red, and near‐infrared perovskite light‐emitting diodes (PeLEDs). However, blue PeLEDs are still far behind in performance, which restricts the development of PeLEDs in practical applications. Herein, a facile energy cascade channel strategy via one‐step self‐organized and controllable 2D/3D perovskite preparation by introducing guanidine hydrobromide (GABr) is developed that greatly improves the efficiency of blue PeLEDs. The 2D/3D perovskite structure boosts the energy cascade to induce energy transfer from the wide into the narrow bandgap domains and inhibit free charge diffusion, which increases the density of electrons and holes, and enhances the radiative recombination. Profiting from this energy cascade channels, the external quantum efficiency of blue PeLEDs, emitting at 492 nm, is considerably enhanced from 1.5% of initial blue device to 8.2%. In addition, device operating stability under ambient conditions is also improved by 2.6‐fold. The one‐step self‐organized 2D/3D hybrid perovskites induced by GABr pave a new and simple route toward high‐performance blue emission PeLEDs.  相似文献   

10.
    
A study of hybrid light‐emitting diodes (HyLEDs) fabricated with and without solution‐processible Cs2CO3 and Ba(OH)2 inorganic interlayers is presented. The interlayers are deposited between a zinc oxide electron‐injection layer and a fluorescent emissive polymer poly(9‐dioctyl fluorine–alt‐benzothiadiazole) (F8BT) layer, with a thermally evaporated MoO3/Au layer used as top anode contact. In comparison to Cs2CO3, the Ba(OH)2 interlayer shows improved charge carrier balance in bipolar devices and reduced exciton quenching in photoluminance studies at the ZnO/Ba(OH)2/F8BT interface compared to the Cs2CO3 interlayer. A luminance efficiency of ≈28 cd A?1 (external quantum efficiency (EQE) ≈ 9%) is achieved for ≈1.2 μm thick single F8BT layer based HyLEDs. Enhanced out‐coupling with the aid of a hemispherical lens allows further efficiency improvement by a factor of 1.7, increasing the luminance efficiency to ≈47cd A?1, corresponding to an EQE of 15%. The photovoltaic response of these structures is also studied to gain an insight into the effects of interfacial properties on the photoinduced charge generation and back‐recombination, which reveal that Ba(OH)2 acts as better hole blocking layer than the Cs2CO3 interlayer.  相似文献   

11.
    
Perovskite light‐emitting diodes (LEDs) require small grain sizes to spatially confine charge carriers for efficient radiative recombination. As grain size decreases, passivation of surface defects becomes increasingly important. Additionally, polycrystalline perovskite films are highly brittle and mechanically fragile, limiting their practical applications in flexible electronics. In this work, the introduction of properly chosen bulky organo‐ammonium halide additives is shown to be able to improve both optoelectronic and mechanical properties of perovskites, yielding highly efficient, robust, and flexible perovskite LEDs with external quantum efficiency of up to 13% and no degradation after bending for 10 000 cycles at a radius of 2 mm. Furthermore, insight of the improvements regarding molecular structure, size, and polarity at the atomic level is obtained with first‐principles calculations, and design principles are provided to overcome trade‐offs between optoelectronic and mechanical properties, thus increasing the scope for future highly efficient, robust, and flexible perovskite electronic device development.  相似文献   

12.
    
Three blue‐light emitting dipyrenylbenzene derivatives, 1‐(4‐(1‐pyrenyl)phenyl)pyrene (PPP), 1‐(2,5‐dimethoxy‐4‐(1‐pyrenyl)phenyl)pyrene (DOPPP), and 1‐(2,5‐dimethyl‐4‐(1‐pyrenyl)phenyl)pyrene (DMPPP), have been prepared by the Suzuki coupling reaction of aryl dibromides with pyreneboronic acid in high yields. These compounds exhibit high glass‐transition temperatures of 97–137 °C and good film‐forming ability. As revealed from single‐crystal X‐ray analysis, these dipyrenylbenzenes adopt a twisted conformation with inter‐ring torsion angles of 44.5°–63.2° in the solid state. The twisted structure is responsible for the low degree of aggregation in the thin films that leads to fluorescence emission of the neat films at 446–463 nm, which is shorter than that of the typical pyrene excimer emission. The low degree of aggregation is also conducive for the observed high fluorescence quantum yields of 63–75%. In organic light‐emitting diode (OLED) applications, these dipyrenylbenzenes can be used as either the charge transporter or host emitter. The non‐doped blue OLEDs that employ these compounds as the emissive layer can achieve a very high external quantum efficiency (ηext) of 4.3–5.2%. In particular, the most efficient DMPPP‐based device can reach a maximum ηext of 5.2% and a very high luminescence of 40 400 cd m–2 in the deep‐blue region with Commission Internationale d'Énclairage (CIE) coordinates of (0.15, 0.11).  相似文献   

13.
    
An enhancement in the external quantum efficiency (QE) of red phosphorescent organic light‐emitting devices (OLEDs) by using facially encumbered and bulky meso‐aryl substituted PtII porphyrin complexes is demonstrated. The maximum external QEs of phosphorescent OLEDs doped with the facially non‐encumbered PtII porphyrin complex 1 [5,15‐bis[4‐(4,4‐dimethyl‐2,6‐dioxacyclohexyl)phenyl]‐2,8,12,18‐tetrahexyl‐3,7,13,17‐tetramethylporphyrin platinum(II )], the facially encumbered PtII porphyrin complex 2 [5,15‐bis(2,6‐dimethoxyphenyl)‐2,8,12,18‐tetrahexyl‐3,7,13,17‐tetramethylporphyrinato platinum(II )], the PtII porphyrin complex 3 that bears bulkier 3,5‐di‐tert‐butylphenyl substituents [5,15‐bis(3,5‐di‐t‐butylphenyl)‐2,8,12,18‐tetrahexyl‐3,7,13,17‐tetramethylporphyrin platinum(II )], and the “doubly‐decamethylene‐strapped” PtII porphyrin complex 4 were 1, 4.2, 7.3, and 8.2 %, respectively. The trend of increasing QE values in the order of 1 < 2 < 3 < 4 may be related to facial encumbrance and steric bulkiness of meso‐aryl substituted PtII porphyrin complexes. Especially, in the case of the PtII porphyrin 4 , it is considered that the “double straps” play an important role in restricting rotational freedom of the meso‐aryl substituents. The triplet excited‐state lifetimes for PtII porphyrins 1 – 4 in OLEDs at an injection current density of 0.55 mA cm–2 were 80, 103, 140, and 152 μs, respectively. We believe that the trend of increasing triplet lifetime in going from 1 to 4 is correlated with suppressing non‐radiative decay.  相似文献   

14.
    
The relatively high sheet resistance of graphene compared with indium tin oxide (ITO) blocks the applications of graphene as transparent electrodes in organic light‐emitting diodes. A novel copper (Cu)/graphene composite electrode is presented and employed as the anode of a top‐emission organic light‐emitting diode with the structure of Cu/graphene/V2O5/NPB/Alq3/Alq3: C545T/Bphen: Cs2CO3/Sm/Au. The Cu/graphene composite electrodes are fabricated by growing graphene directly on Cu substrates via the chemical vapor deposition method without any transfer process. The maxima of current efficiency and power efficiency of a typical Cu/graphene composite anode device reach 6.1 cd/A and 7.6 lm/W, respectively, which are markedly higher than those of the control devices with a graphene anode, a Cu anode or an ITO anode. The low sheet resistance of the composite electrode, the high quality of graphene without any transfer process and the avoidance of wave guiding loss in glass or polyethylene terephthalate substrates result in the improvements of light emission efficiencies.  相似文献   

15.
    
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16.
    
2‐(2‐tert‐Butyl‐6‐((E)‐2‐(2,6,6‐trimethyl‐2,4,5,6‐tetrahydro‐1H‐pyrrolo[3,2,1‐ij]quinolin‐8‐yl)vinyl)‐4H‐pyran‐4‐ylidene)malononitrile (DCQTB) is designed and synthesized in high yield for application as the red‐light‐emitting dopant in organic light‐emitting diodes (OLEDs). Compared with 4‐(dicyanomethylene)‐2‐tert‐butyl‐6‐(1,1,7,7,‐tetramethyljulolidyl‐9‐enyl)‐4H‐pyran (DCJTB), one of the most efficient red‐emitting dopants, DCQTB exhibits red‐shifted fluorescence but blue‐shifted absorption. The unique characteristics of DCQTB with respect to DCJTB are utilized to achieve a red OLED with improved color purity and luminous efficiency. As a result, the device that uses DCQTB as dopant, with the configuration: indium tin oxide (ITO)/N,N′‐bis(1‐naphthyl)‐N,N′‐diphenyl‐1,1′‐biphenyl‐4,4′‐diamine (NPB; 60 nm)/tris(8‐quinolinolato) aluminum (Alq3):dopant (2.3 wt %) (7 nm)/2,9‐dimethyl‐4,7‐diphenyl‐1,10‐phenanthroline (BCP; 12 nm)/Alq3(45 nm)/LiF(0.3 nm):Al (300 nm), shows a larger maximum luminance (Lmax = 6021 cd m–2 at 17 V), higher maximum efficiency (ηmax = 4.41 cd A–1 at 11.5 V (235.5 cd m–2)), and better chromaticity coordinates (Commission Internationale de l'Eclairage, CIE, (x,y) = (0.65,0.35)) than a DCJTB‐based device with the same structure (Lmax = 3453 cd m–2 at 15.5 V, ηmax = 3.01 cd A–1 at 10 V (17.69 cd m–2), and CIE (x,y) = (0.62,0.38)). The possible reasons for the red‐shifted emission but blue‐shifted absorption of DCQTB relative to DCJTB are also discussed.  相似文献   

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19.
    
Light‐emitting electrochemical cells (LECs) have emerged as some of the simplest light‐emitting devices. Indeed, numerous LECs have been produced using fluorescent polymers; however, initial LEC structures require a mixture of polymers and electrolytes, thus strictly limiting their applicability. In contrast, recent advances in device technologies and material synthesis have opened a route for LECs using nonpolymeric materials. This progress report focuses on current developments in the device concepts, mechanisms, and characteristics of LECs that allow the utilization of nonpolymeric materials. First, the three primary device types, namely, electrochemically doped, ionic‐material, and electrostatically doped LECs, are categorized, and their distinct features are described. Second, electrochemically doped LECs based on small molecules and branched molecules are introduced. Then, an overview of the rapidly growing field of ionic‐material LECs, especially ionic transition metal complexes, ionic small molecules and perovskites, and their characteristics are provided. Following these results, recent achievements in solid‐state materials, such as inorganic single crystals, quantum dots, and 2D materials, as electrostatically doped LECs are highlighted. Finally, an overview and evaluation of these LECs reveal the key directions and remaining issues that must be overcome to further functionalize LECs, which provide a versatile approach for new lighting applications comprising emergent materials.  相似文献   

20.
    
The vast majority of conjugated‐polymer‐based light emitting field‐effect transistors (LEFETs) are characterized by low charge‐carrier mobilities typically in the 10−5 to 10−3 cm2 V−1 s−1 range. Fast carrier transport is a highly desirable characteristic for high‐frequency LEFET operation and, potentially, for use in electrically pumped lasers. Unfortunately, high‐mobility organic semiconductors are often characterized by strong intermolecular π–π interactions that reduce luminescence. Development of new materials and/or device concepts that overcome this hurdle are therefore required. Single organic semiconductor layer based LEFETs that combine high hole mobilities with encouraging light emission characteristics are reported. This is achieved in a single polymer layer LEFET, which is further enhanced through the use of a small‐molecule/conjugated polymer blend system that possesses a film microstructure which supports enhanced charge‐carrier mobility (3.2 cm2 V−1 s−1) and promising light‐emission characteristics (1600 cd m−2) as compared to polymer‐only based LEFETs. This simple approach represents an attractive strategy to further advance the performance of solution‐processed LEFETs.  相似文献   

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