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Proceedings Paper

Phosphorescent iridium(III) cored dendrimers for light-emitting displays
Author(s): J.-C. Ribierre; S. V. Staton; P. L. Burn; I. D. W. Samuel
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Paper Abstract

Solution-processable electrophosphorescent dendrimers are an emerging class of materials for highly efficient light-emitting diodes. Here, we report time-resolved photoluminescence measurements in a fac-tris(2-phenylpyridyl)iridium(III) [Ir(ppy)3]-cored dendrimer in neat film and blended into a 4,4'-bis(N-carbazolyl)biphenyl (CBP) host. Our results identify the existence of a photodegradation process that occurs in solution prior to processing, which significantly affects the photoluminescence kinetics of the films and leads to lower external quantum efficiencies of solution-processed phosphorescent dendrimer light-emitting displays. In parallel, we studied the triplet-triplet exciton annihilation processes in these materials from the photoluminescence decays measured at various excitation densities. From the values of the annihilation rates, we calculated the triplet exciton diffusion lengths and estimated the limiting current densities above which annihilation would dominate in phosphorescent dendrimer light-emitting devices. The results show that the triplet exciton diffusion length is small (<15 nm) in phosphorescent dendrimers and that exciton diffusion becomes still slower in the blends, which can be interpreted by the intermolecular spacing between the phosphorescent emitters being increased, thus reducing the annihilation rate.

Paper Details

Date Published: 5 December 2006
PDF: 8 pages
Proc. SPIE 6333, Organic Light Emitting Materials and Devices X, 63330H (5 December 2006); doi: 10.1117/12.683380
Show Author Affiliations
J.-C. Ribierre, Univ. of St. Andrews (United Kingdom)
S. V. Staton, Univ. of Oxford (United Kingdom)
P. L. Burn, Univ. of Oxford (United Kingdom)
I. D. W. Samuel, Univ. of St. Andrews (United Kingdom)

Published in SPIE Proceedings Vol. 6333:
Organic Light Emitting Materials and Devices X
Zakya H. Kafafi; Franky So, Editor(s)

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