Development of dendrimers: Macromolecules for use in organic light-emitting diodes and solar cells
Department of Chemistry, University of Oxford, Chemistry Research Laboratory, 12 Mansfield Road, Oxford OX1 3TA, United Kingdom.Chemical Reviews (Impact Factor: 45.66). 05/2007; 107(4):1097-116. DOI: 10.1021/cr050136l
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ABSTRACT: A facile synthesis has been demonstrated for the first time to construct self-host functional Ir-cored dendrimers up to the fourth generation on the basis of a newly developed polyether dendron, where the N-phenylcarbazole (NPC) moiety is used as the basic building block instead of benzene to improve charge transport whilst keeping the ease of preparation. With the growing generation number, the dendrimer size can be well tuned in a wide range of 4–10 nm. The obtained fourth generation dendrimer 45NPC-G4 is the largest Ir complex ever reported so far, having a diameter up to 10 nm and a molecular weight as high as 15.9 kDa. Most interestingly, the performance of non-doped phosphorescent organic light-emitting diodes (PhOLEDs) is found to be greatly dependent on the molecular size. For example, 9NPC-G2 (R ≈ 30 Å) reveals the best luminous efficiency as high as 50.5 cd A−1 (56.6 lm W−1, 14.8%), whereas the efficiency of 45NPC-G4 (R ≈ 50 Å) sharply drops to 10.5 cd A−1 (5.6 lm W−1, 3.4%). The results suggest that an appropriate size of 6 ± 2 nm is desirable to balance the dilemma between luminescence quenching and charge transport, and thereby realize highly efficient non-doped PhOLEDs.02/2015; 6(7). DOI:10.1039/C4PY01332H
Annual Review of Materials Research 08/2014; 45(1):150421150026007. DOI:10.1146/annurev-matsci-070214-021113 · 15.63 Impact Factor
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ABSTRACT: Novel fully conjugated push-pull dendrons were synthesized by a divergent approach to evaluate the performance of non-conventional architectures like dendritic one in charge separation processes associated with photovoltaic events. The dipole moments in excited state were estimated by the solvatochromic method, to be related to the charge separation efficiency. A 1:2 ratio of donor-acceptor groups (methoxy and nitro groups respectively) promotes the largest dipole moment in both ground and excited state (up to 17 D), due to the efficient electron density transfer over the entire molecule, through the π-electron system. The synthesized dendrons induce charge transfer on excitation as follows from UV-vis absorption-emission analysis and theoretical calculations.Journal of Physical Organic Chemistry 04/2015; 28(4):304-311. DOI:10.1002/poc.3411 · 1.23 Impact Factor
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