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1594821 
Journal Article 
Is Poly(vinylcarbazole) a Good Host for Blue Phosphorescent Dopants in PLEDs? Dimer Formation and Their Effects on the Triplet Energy Level of Poly(N-vinylcarbazole) and Poly(N-Ethyl-2-Vinylcarbazole) 
Jankus, V; Monkman, AP 
2011 
Yes 
Advanced Functional Materials
ISSN: 1616-301X
EISSN: 1616-3028 
21 
17 
3350-3356 
WOS:000295184400019 
The detailed measurement and analysis of the delayed
emission from poly(vinylcarbazole) (PVK) and poly(N-ethyl-2-vinyl-carbazole) (P2VK) thin films is
described. PVK has rapidly become a ""polymer of choice"" for hosting phosphorescent dopants in
PLEDs, especially blue emitters. In this respect it is important to have a full understanding of
the triplet properties of this host. It is concluded that in films, the electronic 0-0 peak
energy of PVK phosphorescence is found at 2.88 eV (14 K). With an increase of temperature, >44 K,
increasing emission from new long lived, lower energy species, previously ascribed to ""trap
states"" in the literature, is observed. Increasing temperature enables thermally assisted
triplet exciton hopping to these trap states. Critically it is shown that some of these triplet
trap species are ground state triplet dimers in origin for both PVK (2.46 eV) and P2VK (2.1 eV),
and not all of them are of excimer nature as previously thought. These species can quench the
emission of blue heavy metal complexes doped in PVK and drastically effect performance over
lifetime if the dimer formation increases over time and at elevated operating temperature. It is
therefore concluded that PVK might not be such an ideal host material for blue phosphorescent
emitters.