Highly Efficient Light-Harvesting System Based on a Phosphorescent Acceptor Coupled with Dendrimer Donors via Singlet−Singlet and Triplet−Triplet Energy Transfer

A series of efficient light-harvesting systems (FIr3mGx, x = 1−3) based on dendrimer donor (mCP:  N,N‘-dicarbazolyl-3,5-benzene) derivatives coupled with a sky blue phosphorescent acceptor (FIrpic:  iridium(III) bis[(4,6-difluorophenyl)pyridinato-N,C 2‘]-3-hydroxypicolinate derivative) were prepared...

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Published in:Chemistry of materials 2007-07, Vol.19 (15), p.3673-3680
Main Authors: Kwon, Tae-Hyuk, Kim, Myoung Ki, Kwon, Jongchul, Shin, Dae-Yup, Park, Su Jin, Lee, Chang-Lyoul, Kim, Jang-Joo, Hong, Jong-In
Format: Article
Language:English
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Summary:A series of efficient light-harvesting systems (FIr3mGx, x = 1−3) based on dendrimer donor (mCP:  N,N‘-dicarbazolyl-3,5-benzene) derivatives coupled with a sky blue phosphorescent acceptor (FIrpic:  iridium(III) bis[(4,6-difluorophenyl)pyridinato-N,C 2‘]-3-hydroxypicolinate derivative) were prepared, and their photophysical properties were investigated. The light-harvesting ability of FIr3mGx (x = 1−3) increases with the number of energy donor mCP units. The acceptor PL intensity of the donor−acceptor conjugate dendrimers (FIr3mGx, x = 1−3) increases over 6 times with the number of mCP units via sensitization from the light-harvesting antenna after excitation at the donor absorption (λex = 310 nm), as compared to that of only an acceptor without a donor (FIrpic) upon excitation at the MLCT region (λex = 380 nm) because of efficient intramolecular singlet−singlet and triplet−triplet energy transfer from the donor to the acceptor and less luminance quenching induced by the bulky dendrimer structure. The singlet−singlet intramolecular energy transfer in FIr3mGx from the dendrimer donor to the acceptor exhibits a high efficiency of greater than 90% via the steady-state PL method and 94% via the transient PL method. Additionally, the triplet−triplet energy transfer efficiency via the transient PL method exhibits an efficiency greater than 99%. This indicates that FIr3mGx exhibits good light-harvesting abilities because the mCP unit is an efficient light absorber and because the core FIrpic functions as a spatial energy concentrator that drains energy from the dendrimer donor.
ISSN:0897-4756
1520-5002
DOI:10.1021/cm070536k