Mixed (difluoro)phenylpyridine/(difluoro)phenylpyrazole tris-cyclometalated iridium complexes were prepared in order to study the effect of fluorination and the pyridine/pyrazole ratio on the emission and electrochemical properties. Increasing fluorination and replacement of pyridine by pyrazole both leads to a widening of the HOMO-LUMO gap and generally leads to a blue shift in emission.
The preparation of spherical phosphor (Y 2 O 3 :Eu) particles that are monosized for a given set of conditions, are described. The nature of the resulting self-assembled and close packed phosphor spherical particles appears to be very promising for both field emission devices (FED) and high definition television (HDTV). The size of the particles can be controlled by careful manipulation of the experimental conditions, the rationale behind this is discussed. The luminescent efficiency of the particles as a function of particle size is also reported. It is demonstrated that good light output is possible from nanocrystals.
The synthesis, structure, and photophysical and electrochemical properties of cyclometalated iridium complexes with ancillary cyano and isocyanide ligands are described. In the first synthetic step, cleavage of dichloro-bridged dimers [Ir(N=C)2(mu-Cl)]2 (N=C = 2-phenylpyridine, 2-(2-fluorophenyl)pyridine, and 2-(2,4-difluorophenyl)pyridine) by isocyanide ligands gave monomeric species of the types Ir(N=C)2(RNC)(Cl) (RNC = t-butyl isocyanide, 1,1,3,3-tetramethylbutyl isocyanide, 2-morpholinoethyl isocyanide, and 2,6-dimethylphenyl isocyanide). In turn, the chloride was replaced by cyanide giving Ir(N=C)2(RNC)(CN). The X-ray structures for two of the complexes show that the trans-pyridyl/cis-phenyl geometry of the parent dimer is preserved, with the ancillary ligands positioned trans to the cyclometalated phenyls. The cyano complexes all display strong blue photoluminescence in ambient, deoxygenated solutions with the first lambdamax ranging from 441 to 458 nm, quantum yields spanning 0.60 to 0.75, and luminescent lifetimes of 12.0-21.4 mus. A lack of solvatochromism and highly structured emission indicate that the lowest energy excited state is triplet ligand centered with some admixture of singlet metal-to-ligand charge-transfer character.
Thin-film Y3−xAl5O12:Tbx3+ (YAG:Tb) phosphor derived from a sol-gel chemistry is analyzed by x-ray diffraction, scanning electron microscopy, photoluminescence (PL) and cathodoluminescence (CL). The metal alkoxides organic precursors were chosen as the starting materials to form the sol-gel. This liquid sol-gel was spin coated on sapphire and silicon substrates to form the uniform thin films, then crystallized by annealing. The PL intensity of the crystallized film at 545 nm green emission was 15 times higher than that of the as-coated noncrystalline film. CL measurements show that luminance and efficiency are comparable to the films deposited by other techniques.
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