Ultrafast photogeneration mechanisms of triplet states in para-hexaphenyl

Date
1999-06Author
Zenz, C.
Cerullo, G.
Lanzani, G.
Graupner, W.
Meghdadi, F.
Leising, G.
De Silvestri, S.
Metadata
Show full item recordAbstract
We present femtosecond pump-probe measurements, both conventional and electric field-assisted, on organic light-emitting devices based on para-hexaphenyl. The dominant triplet excition generation mechanism is assigned to nongeminate bimolecular recombination of photogenerated, spin-1/2 polarons. This process is active within a few hundred femtoseconds after photoexcitation and involves about 20% of the initially excited states. At higher photoexcitation densities, we observe an additional triplet generation mechanism, which occurs in the 10-ps time domain, due to fusion of singlet excitons and subsequent fission into correlated triplet pairs. The latter decay on the 10(2)-ps time scale by geminate recombination.
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- Scholarly Works, Physics [886]