期刊
CHEMISTRY-A EUROPEAN JOURNAL
卷 17, 期 32, 页码 8947-8956出版社
WILEY-V C H VERLAG GMBH
DOI: 10.1002/chem.201100695
关键词
electrophosphorescence; molecular devices; molecular electronics; phosphine oxide; short-axis substitution
资金
- National Key Basic Research and Development Program of China [2010CB327701]
- NSFC [50903028, 60977024]
- Natural Science Foundation of Heilongjiang province [QC08C10]
- Education Bureau of Heilongjiang province [2010td03]
- Heilongjiang University [2010 hdtd-08]
An efficient host for blue and green electrophosphorescence, 4,6-bis(diphenylphosphoryl) dibenzofuran (o-DBFDPO), with the structure of a short-axis-substituted dibenzofuran was designed and synthesised. It appears that the greater density of the diphenylphosphine oxide (DPPO) moieties in the short-axis substitution configuration effectively restrains the intermolecular interactions, because only very weak pi-pi stacking interactions could be observed, with a centroid-to-centroid distance of 3.960 angstrom. The improved thermal stability of o-DBFDPO was corroborated by its very high glass transition temperature (T-g) of 191 degrees C, which is the result of the symmetric disubstitution structure. Photophysical investigation showed o-DBFDPO to be superior to the monosubstituted derivative, with a longer lifetime (1.95 ns) and a higher photoluminescent quantum efficiency (61%). The lower first singlet state excited level (3.63 eV) of o-DBFDPO demonstrates the stronger polarisation effect attributable to the greater number of DPPO moieties. Simultaneously, an extremely high first triplet state excited level (T-1) of 3.16 eV is observed, demonstrating the tiny influence of short-axis substitution on T-1. The improved carrier injection ability, which contributed to low driving voltages of blue- and green-emitting phosphorescent organic light-emitting diodes (PHOLEDs), was further confirmed by Gaussian calculation. Furthermore, the better thermal and morphological properties of o-DBFDPO and the matched frontier molecular orbital (FMO) levels in the devices significantly reduced efficiency roll-offs. Efficient blue and green electrophosphorescence based on the o-DBFDPO host was demonstrated.
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