The organic materials used in electronic and optoelectronic devices fall into two groups: small molecules and polymers. The former are typically deposited by vapor methods in low or high vacuum environments and have a well-defined molecular weight. The latter must be processed from solution and have a molecular weight distribution that is described by the polydispersity of the materials, giving polymers good glass-forming and mechanical properties. Dendrimers are a class of materials that in some ways fall between molecular and polymeric materials. This paper discusses the construction of dendrimers, including the use of the core-branch structure of dendrimers to control the properties of the materials on the nanometer scale as well as their use in organic light emitting diodes (LEDs) and solar cells.
"Recently, much effort has been devoted to the development of new amorphous non-doped materials possessing high morphological stability  . Dendrimer is as an alternative class of amorphous molecular electroluminescent (EL) materials . Unlike small molecules and polymers, the prettiness of dendrimers is that their light emission can be finely tuned by the selection of the core, solubility can be adjusted by selecting the proper surface groups and level of intermolecular interactions can be controlled by the type and generations of the dendrons employed, that are vital part to OLEDs performance  . "
[Show abstract][Hide abstract] ABSTRACT: A series of new N-coumarin dyes containing oligothiophenyl N-coumarins as cores and carbazole dendrons up to the third generation as substituents were synthesized and characterized. Their optical, thermal, electrochemical, and electroluminescent properties as non-doped solution-processed hole-transporting light-emitters for electroluminescent devices were investigated. It was found that by incorporating carbazole dendrons in the molecule, we were able to reduce the crystallization and maintain the high emissive ability of a planar N-coumarin fluorescent core in the solid state as well as improve the thermal stability of the material. These N-coumarins showed a bright green fluorescence and could form morphologically stable amorphous thin films with glass-transition temperatures as high as 299 °C. Simple structured solution-processed organic light-emitting diodes using these dyes as emissive layers emitted a stable green electroluminescence (λEL = 517 nm) with high luminance efficiencies (up to 9.45 cd A-1 at 6.7 mA cm-2) and high green color purity.
Dyes and Pigments 01/2015; 112:227–235. DOI:10.1016/j.dyepig.2014.06.032 · 3.97 Impact Factor
"The structural characterization of these highly complex structures and their interaction mechanisms are ongoing challenges. Dendrimers, spherical and mono-disperse polymers with a tree-like or generational structure, have generated a tremendous interest for many applications ranging from materials science to biomedical applications   . Dendrimers have internal cavities and functional end groups which can interact with small molecules increasing their solubilities. "
[Show abstract][Hide abstract] ABSTRACT: The interaction of poly(amidoamine)-G3 (PAMAM-G3) dendrimer with nicotinic acid (NA) was investigated by using molecular dynamics (MD) simulations. First, sample free energy profiles of NA crossing PAMAM-G3 at pH 6 and 3 were computed using the adaptive biasing force (ABF) method. We found that PAMAM-G3 provides a more appropriate environment for NA inclusion when internal tertiary amine groups are unprotonated (at pH 6). However, when internal tertiary amine groups are protonated (at pH 3), the PAMAM cavities are less hydrophobic; therefore the drug-dendrimer interactions become similar to drug-solvent interactions. Traditional MD simulations were also performed to investigate the structural stability of the PAMAM-NA complexes near the free energy minima at pH 6. We found that association of NA and PAMAM adopts a preferred binding mode around the surface of PAMAM, where hydrogen bond (HB) interactions with the amino and amide NH groups of the nearby monomers are established. These interactions are very stable whether additional van der Waals interactions between pyridine ring of NA and methylene groups of the more external monomers of PAMAM are established.
"Organic semiconducting materials have been the subject of intense research interest for low cost, lightweight, portable and flexible device applications, particularly for organic field effect transistors (OFETs)    , organic photovoltaics (OPVs)    , and organic light emitting diodes (OLEDs)  . Conjugated polymers, dendrimers   and poly(dendrimers)      can be solution processed at low cost by spin coating or ink-jet printing  . In this context, diketopyrrolopyrrole (DPP) based narrow optical gap polymers are promising materials for photovoltaic applications    . "
[Show abstract][Hide abstract] ABSTRACT: a b s t r a c t A new thieno[3,2-b]thiophenediketopyrrolopyrrole-benzo[1,2-b:4,5-b 0 ]dithiophene based narrow optical gap co-polymer (PTTDPP-BDT) has been synthesized and characterized for field-effect transistors and solar cells. In field-effect transistors the polymer exhibited ambipolar charge transport behaviour with maximum hole and electron mobilities of 10 À3 cm 2 V À1 s À1 and 10 À5 cm 2 V À1 s À1 , respectively. The respectable charge transporting properties of the polymer were consistent with X-ray diffraction measurements that showed close molecular packing in the solid state. The difference in hole and electron mobilities was explained by density functional theory calculations, which showed that the highest occupied molecular orbital was delocalized along the polymer backbone with the lowest unoccupied molecular orbital localized on the bis(thieno[3,2-b]thiophene)dike-topyrrolopyrrole units. Bulk heterojunction photovoltaic devices with the fullerene accep-tor PC 70 BM were fabricated and delivered a maximum conversion efficiency of 3.3% under AM1.5G illumination.
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