High efficiency deep blue phosphorescent organic light-emitting diodes using a double emissive layer structure

High efficiency deep blue phosphorescent organic light-emitting diodes (PHOLEDs) have been developed with a double emissive layer structure (D-EML). Using bis(4′,6′-difluorophenylpyridinato)tetrakis(1-pyrazolyl)borate (FIr6) as an electro-phosphorescent dopant, we achieved a maximum external quantum efficiency of 14.8% in the deep blue PHOLEDs with D-EMLs, which is 50% higher value than that of 9.76% with single emissive layer structure (S-EML). Moreover, the external quantum efficiency at high current density region of 10 mA/cm² was maintained up to 11.3% in this D-EML device. We attributed this enhancement to the expansion of carrier recombination region and the effective confinement of exciton within the emissive layer.     

A new polyfluorene containing repeated ethylenoxy units linked to glycerol as side chains: Synthesis and application as an electron injection material in the fabrication of polymer light-emitting diodes

A new polyfluorene derivative (PF-GOH) containing repeated ethylenoxy units linked to glycerol as side chains was synthesized as an electron injection material. The polymer was not very soluble in methanol, but reasonably soluble in mixed solvents such as methanol/ethylene glycol (EG) and isopropyl alcohol (IPA)/EG. Polymer light-emitting diodes (PLEDs) were fabricated with a ITO/PEDOT:PSS/MEH-PPV/PF-GOH/Al configuration. The PLEDs exhibited significantly improved performance in the presence of the PF-GOH layer compared to the device without the electron injection polymer layer. The performance of the PLEDs was largely dependent on the solvent systems employed. Among methanol, methanol/EG (3:1), and IPA/EG (1:1), the best performance was obtained when IPA/EG (1:1) was used. The improved performance was attributed to the more uniform thickness of the electron injection layer of PF-GOH, leading to much less current leakage.     

Improved efficiency in red phosphorescent organic light-emitting devices using double doping structure

Light emission efficiency of red phosphorescent organic light-emitting diodes was improved by using a double doping structure in light emitting layer. Red devices with tris(2-phenylpyridine) iridium (Ir(ppy)₃) as a co-dopant for tris(1-phenylisoquinoline) iridium (Ir(piq)₃) showed higher efficiency than Ir(piq)₃ device. Ir(ppy)₃ acted as a sensitizer for energy transfer from (4,4′-N,N′-dicarbazole)biphenyl to Ir(piq)₃ and enhanced luminance efficiency of Ir(piq)₃ by 30%.     

Bistability and improved hole injection in organic bistable light-emitting diodes using a quantum dot embedded hole transport layer

Organic bistable light-emitting diodes (OBLED) were developed by using a quantum dot embedded hole transport layer in the organic light-emitting diodes. The driving voltage of the OBLED was decreased due to the good hole transport properties of quantum dot embedded hole transport layer and the OBLED also showed bistability at negative bias due to the switching behavior of the quantum dot based hole transport layer. The origin for the switching behavior of the OBLED was confirmed by fabricating organic bistable device with the quantum dot embedded hole transport layer.     

Color stable and interlayer free hybrid white organic light-emitting diodes using an area divided pixel structure

Color stable and interlayer free hybrid white organic light-emitting diodes were fabricated by using an area divided pixel structure. The area divided pixel structure was realized by stacking red and blue emitting layers using a fine metal mask. A phosphorescent red emitting layer was patterned by a metal mask and a blue fluorescent emitting layer was commonly deposited on the patterned red emitting layer. The blue fluorescent emitting layer could play a role of a hole-blocking layer and a white emission could be obtained due to separate emission of red and blue emitting layers. The interlayer free hybrid WOLEDs showed color stability from 100 cd/m² to 10,000 cd/m².     

Air stable and low temperature evaporable Li3N as a n type dopant in organic light-emitting diodes

N doped organic light-emitting diodes were developed by using Li₃N as a n type dopant in electron transport layer. Driving voltage was greatly lowered by using Li₃N doped electron transport layer and combination of MoO₃ doped hole transport layer with Li₃N doped electron transport layer gave high quantum efficiency of 15% and low driving voltage of 4 V at 1000 cd/m² in green phosphorescent organic light-emitting diodes. Decomposition of Li₃N during evaporation into Li and N₂ was found to be responsible for n doping effect of Li₃N.     

High color rendering white organic light-emitting diodes fabricated using a broad-bandwidth red phosphorescent emitter for lighting applications

High color rendering white organic light-emitting devices (WOLEDs) were developed using a broad-bandwidth red phosphorescent iridium complex, bis[2-(1-naphthyl)benzothiazolato-N,C²′]iridium(III) acetylacetonate [Ir(absn)₂(acac)]. The red phosphorescent emitter Ir(absn)₂(acac) was used to fabricate blue–red and blue–green–red WOLEDs by combining blue-emitting bis[2-(4,6-difluorophenyl)pyridinato-N,C²′]iridium(III) picolinate (FIrpic) and green-emitting tris-fac-(2-cyclohexenylpyridine) iridium (III) [Ir(chpy)₃] in multiple-emissive layers. Mixed host emissive layers were employed using a hole-transport-type host 4,4′,4″-tris(N-carbazolyl)triphenylamine (TCTA) and an electron-transport-type host 2,6-bis[3-(carbazol-9-yl)phenyl]pyridine (DCzPPy) for efficient charge carrier injection. Di-[4-(N,N-ditolyl-amino)-phenyl]cyclohexane (TAPC) and 1,3-bis(3,5-dipyrid-3-yl-phenyl)benzene (BmPyPB) were used as the hole and electron transporting layers, respectively. The effects of the emissive layer thickness and the doping ratios of different color dopants on WOLED performances were investigated. The WOLED based on ITO/TAPC/TCTA:FIrpic (10%):Ir(absn)₂(acac) (4%)/TCTA:Ir(chpy)₃ (9%, 6 nm)/DCzPPy:FIrpic (13%):Ir(absn)₂(acac) (4%)/BmPyPB/LiF/Al exhibited an external quantum efficiency of 10.7%, a power efficiency of 23.0 lm/W, a very high color rendering index (CRI) of 88.1, and a correlated color temperature (CCT) of 2629 K at 1000 cd/m².     

Efficiency improvement of blue phosphorescent organic light emitting diodes by using a stacked emitting structure

Quantum efficiency of blue phosphorescent organic light emitting diodes (PHOLEDs) was improved by using a stacked emitting structure which can balance holes and electrons in light emitting layer. N,N′-dicarbazolyl-3,5-benzene (mCP) doped with iridium(III) bis(4,6-(di-fluorophenyl)-pyridinato-N,C2′) picolinate (FIrpic) was used as an emitting layer with good hole injection properties near hole transport layer and 1,3-bis(triphenylsilyl)-benzene (TSB) doped with FIrpic was used as an emitting layer with good electron injection properties near electron transport layer. High quantum efficiency of 10.2% was obtained at 500 cd/m² compared with 7.5% and 7.6% of mCP and TSB reference devices.     

Broad band and white phosphorescent polymer light-emitting diodes in multilayer structure

Efficient phosphorescent polymer light-emitting diode with poly(vinylcarbazole) (PVK) doped by two or three iridium complexes in single and bilayer structures are studied. With (tris-(2-4(4-toltyl) phenylpyridine) (Ir(mppy)₃) as the green emitter and (1-phenylisoquinoline) (acetylacetonate) iridium(III) (Ir(piq)₂) as the red emitter the efficiency is as high as 23 cd/A with broad band emission from 500 nm to 720 nm. For white emission a second layer is added with blue emitter ((III) bis[(4,-6-di-fluorophenyl-pyridinato)N,C²] picolinate) (FIrpic) doped in PVK. White light containing three spectral peaks results with efficiency 8.1 cd/A. As the second blue layer is replaced by the fluorescent (poly(9,9-dioctylfluorene)) (PFO) white emission with high color rendering index 86 is achieved. The efficiency is 5.7 cd/A with peak luminance 8900 cd/m². For a given iridium complexes ratio the relative intensity of the green and red emission depends sensitively on the second blue layer.     

Effects of gas injection condition on mixing efficiency in the ladle refining process

The aim of this research was to investigate the effects of injection condition on the mixing efficiency of the gas injection treatment of the ladle refining process in steelmaking. A water modeling approach was employed. A NaCl solution was injected into the vessel and the electric conductivity value of the water solution was measured to represent the concentration of the additive. The results of this investigation reveal that up to a certain level, mixing efficiency is improved as the gas flow rate increases. Off- center injection is better than centerline injection. However, the injection lance should not be too close to the wall. Also, mixing efficiency is improved when the submerged depth of the immersion lance increases. The immersion hood has a optimal size as far as mixing efficiency is concerned. A larger or smaller hood would reduce its efficiency. The submerged depth of the immersion hood should be kept to a minimum to improve mixing efficiency.     

注塑模抽芯油缸的选取和使用

介绍了液压油缸在注塑模具中常见的抽芯及顶出结构，并对选取油缸的计算方法和使用要点进行阐述。该类机构运行安全可靠，自动化程度高，为油缸在注塑模抽芯及项出机构设计中的选用和使用提供了参考。