Branching OLEDs

Hydrocarbons are ubiquitously in the environment. Natural hydrocarbons range widely in size from methane to /3-carotene (Fig. 2.12) many other branched, ole-finic, cyclic, and aromatic hydrocarbons are found in fossil fuels, or tend to derive... 

This has been found to be a general reaction for many types of olefins. It has also been applied to highly branched structures, such as 2,4,4-trimethyl-2-pen-tane and propylene trimers and tetramers [177], to unbranched olefins with internal double bonds, such as methyl oleate [178] and tricosane, and to a-ole-fins [179], In all cases the data indicate that the reaction occurs at the double... 

A new branched carbazole derivative with phenyl ethylene moieties attached, l,3,5-tris(2-(9-ethylcarbazyl-3)ethylene)benzene (TECEB, 41) (Scheme 3.15), was prepared as a HTM for OLEDs [86], TECEB has a HOMO energy level of —5.2 eV and hole-drift mobility of 1(T 4 cm2/(V s), comparable to NPD. The device performance (maximum luminance of about 10,000 cd/m2 and current efficiency of 3.27 cd/A) in a standard HTL/tris-(8-hydroxyquino-line) aluminum double-layer device is also comparable to NPD, but TECEB has a higher Tg (130°C) and its ease of synthesis is superior to NPD. Distyryl units linked to a TPD derivative, A, A"-bis(4-(2,2-diphenylethenyl)-phenyl)-jY,jV -di(p-tolyl)-bendidine (DPS, 42) (Scheme 3.15), reported by Yamashita and coworkers, showed good hole transport properties and improved thermal stability compared with the parent TPD [87]. 

During the long history of FT synthesis, various approaches have been developed to control product selectivity. Parameters like temperature, pressure, H. CO ratio, conversion, space velocity and alkalization of iron catalysts influence chain length, chain branching, (he ole fin/paraffin ratio and the alcohol selectivity as well as carbon deposition and methane selectivity. The effect of the different parameters can be obtained from Table IV 9]. As a typical example for the... 

Indeed, spin statistics mandate that if the rates of reactions (1) and (2) are the same, then the nongeminate polaron pairs generated by carrier injection in OLEDs would yield 3 TEs for every SE. This SE/TE branching ratio is one of the most important factors suppressing the efficiency of OLEDs based on the fluorescent decay of SEs. However, recent studies suggest that in luminescent -conjugated polymers the rate of reaction (1) is higher than that of (2), so the yield of SEs is... 

We have considered so far only copolymerization of bifimctional vinyl monomers. However, if any of the monomers in the copolymerization is a divinyl compound or any other ole rue monomer with functionabty greater than 2, a branched polymer can result and, furthermore, the growing branches can intercormect to form an in nite crosslinked network known as gel . It is useful to be able to predict the conditions imder which such gel formation will occur. 

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