Conjugated OLEDs

Since acrylonitrile has a strong electronegative substituent (—CN), it can be polymerized by the relatively weak sodium methoxide (NaOCHs) and vinylidene cyanide carrying two —CN groups on the same carbon atom can be polymerized even by weaker bases like water and amines. However, for polymerization of nonpolar monomers such as conjugated ole ns very strong bases like metal alkyls should be used as initiators. 

Single layer OLEDs have been fabricated with a variety of emitter molecules and conjugated polymers such as poly(phenylene vinylene) (PPV). 

There have been numerous studies of the electrical and emission properties of conjugated polymer-, small molecule-, and molecularly doped polymer-based OLEDs. The current-voltage and radiance-voltage characteristics have been nica sured as a function of thickness of the organic layer, temperature, different metal electrodes, etc. in an attempt to understand the device physics. A major factor in hibiting progress is the purity of the organic impurities that are incorporated dur-... 

In electroluminescent applications, electrons and holes are injected from opposite electrodes into the conjugated polymers to form excitons. Due to the spin symmetry, only the antisymmetric excitons known as singlets could induce fluorescent emission. The spin-symmetric excitons known as triplets could not decay radiatively to the ground state in most organic molecules [65], Spin statistics predicts that the maximum internal quantum efficiency for EL cannot exceed 25% of the PL efficiency, since the ratio of triplets to singlets is 3 1. This was confirmed by the performance data obtained from OLEDs made with fluorescent organic... 

The merit of these chromene dopants is their relatively long emission wavelength peaks compared to DCM or DCJTB materials due to the more conjugated chromene moiety, and this contributes to the more saturated red emission. In fact the EL spectra of OLED devices of ITO/TPD/Alq3 chromene-dopants/Alq3/Mg Ag exhibited satisfactory red emission color, especially for Chromene-1 and Chromene-2 dopants. However, these chromene-based red emitters showed lower fluorescent quantum yield (18%, 15%, and 54% for Chro-... 

Recently, Chen s group reported a deep blue OLED based on an asymmetric mono(styryl) amine derivative DB1 (192) as shown in Scheme 3.59. PL spectra of this deep blue dopant in toluene solution showed a peak emission of 438 nm, which is about 20 nm hypsochromic shift compared with DSA-amine symmetric dopant, due to the shorter chromophoric conjugated length of the mono(styryl) amine. OLED device based on this blue dopant achieved a very high efficiency of 5.4 cd/A, with CIE coordinates of (0.14, 0.13) [234]. 

In sheep orally dosed with 40 mg/kg bw radiolabeled thiophanate, only the parent drug and its major metabolite lobendazole could be detected in plasma for 65 h after dosing. In sheep liver, thiophanate was metabolized to lobendazole at a rate of approximately 34%. Other metabolites included 2-aminobenzimidaz-ole, low molecular-weight aliphatic acids, and limited amounts of the glucuronide and sulfate conjugates. 

The use of transition or rare earth metal complexes as emitting materials for OLED has attracted much attention recently because of the enhancement in EL efficiency from triplet excited state.16 Chan and co-workers demonstrated that incorporation of ruthenium bipyridyl complexes into conjugated polymers would enhance the charge carrier mobilities.17 Through attachment of different transition metal complexes onto polymer chains, tuning of light-emitting properties could be achieved.18... 

---