OLED materials

OLEDs are obviously able to produce light with virtually every color in the CIE chromaticity diagram but the optimum inexpensive method to manufacture a pixeiatcd full color display is not yet established. The difficulty lies in patterning OLED materials with standard photolithographic methods. Five schemes to achieve color have been suggested, as illustrated schematically in Figure 13-19. 

The analytic theory outlined above provides valuable insight into the factors that determine the efficiency of OI.EDs. However, there is no completely analytical solution that includes diffusive transport of carriers, field-dependent mobilities, and specific injection mechanisms. Therefore, numerical simulations have been undertaken in order to provide quantitative solutions to the general case of the bipolar current problem for typical parameters of OLED materials [144—1481. Emphasis was given to the influence of charge injection and transport on OLED performance. 1. Campbell et at. [I47 found that, for Richardson-Dushman thermionic emission from a barrier height lower than 0.4 eV, the contact is able to supply... 

The redispersion microreactor is applied for the liquid-liquid polycondensation to yield an OLED material by multiple Suzuki coupling. As the initial test reaction, the following single Suzuki coupling is currently being explored in the liquid-liquid system made from water/ dioxane/toluene. 

If there is one clear need in the field of OLED materials it continues to be in the area of blue emitters. A blue emissive material with good color coordinates CIE (0.10, <0.10) coupled with long device lifetime (>10,000 h) and high electrical efficiency (>5 cd/A) is the holy grail of materials chemists in this field. A major effort to find such materials continues in many laboratories including our own and the current sets of available materials may be supplanted at any time. However, the current best candidate blue emitters in the SMOLED area compromise many desirable properties — the most troublesome being long lifetime. 

SW Yin, Z Shuai, and Y Wang, A quantitative structure-property relationship study of the glass transition temperature of OLED materials, J. Chem. Inf. Comput. Sci., 43 970-977, 2003. 

Patent Numbers and Titles of the U.S. Patents on the OLED Materials Granted to Idemitsu Kosan... 

Table 11.6 lists the U.S. patent numbers and the titles granted to Idemitsu Kosan on the OLED materials. 

Synopsis of Halls and Schlegel (2001) Molecular Orbital Study of the First Excited State of the OLED Material f 75 (8-hydroxyquinoline)aluminum(ni) . 

A theoretical work on the photophysical properties of 353 appeared (06CPL(429)180). 353 can be a promising OLED material in view of its luminous efficiency and transfer rate. Substituted analogs of 353 have been reported showing an absorption band at 431 nm and an emission at 486 and 516 nm (0F 0.27) (01JCS(P1)740). 

TABLE 1.1. Values of the Glass Transition Temperature Tg, the HOMO and LUMO Levels (Relative to the Vacuum Level), and Typical Hole and Electron Mobilities (fj,h and fie, respectively) at Fields F of 105-106 V/cm of some Typical OLED Materials... 

Based on the Tang s excellent work, the authors examined various combinations of organic molecules and proposed new OLED device structures.32-36 In particular, the discovery of unipolar electron-transport materials, 2-(4 -biphenyl)-5-(4"ferf-butylphenyl)-l,3,4-oxadiazole (PBD), greatly expanded the possibilities of OLED materials and cell structures. Thus, we could classify OLED cell structures into three categories.37 A detailed classification of cell structures is described in Sections 3 and 4. 

These guidelines are common to all OLED materials. Many researchers have encountered these problem, and organic synthesis tailor-made for OLED materials was examined. 

The crystallization of constituent OLED materials is likely to facilitate most of the extrinsic failure modes. If the cathode conforms to the volume shrinkage in the film that occurs with aging and/or crystallization, uneven charge injection... 

Further, introduction of new technological concepts like electrical doping of transport layers has enhanced the OLED efficiency to more than 100 Im/W and enhanced life time of the devices to more than 100,000 hours which is better than the gas filled discharge lamps (Murano et al 2005). However, efficiency and lifetime are still considered widely as the big obstacles on the road of OLED development. A further impa-ovement in the OLED performance relies on the more detailed xmderstanding of the EL physics and the new development in the OLED materials, structure and fabrication. 

When is comes to depositing several layers from organic solvents, however, very often complete nonsolubility cannot be reached, leading to intermixing of the components at the interface. Furthermore, the number of layers is very limited, since only very few solvents can be used to dissolve typical OLED materials. 

Figure 23 Energy level diagrams for OLED materials. Only the frontier orbitals are considered, (a) Transition from the molecular orbital energies to narrow bands in the solid state to the parallelogram image of the HOMO and LUMO energies are shown, (b) The effect of an applied bias on the energy levels (left). The red arrows illustrate carrier injection via tunneling (tu), thermionic emission (te), or midgap states (mg). The midgap states are shown in blue.

Manutiicturer Screen diagonal (inches) OLED Material Structuring Pixel number Date of publication... 

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