Understanding of Energy Transfer Dynamics in Luminescent Eu(III) Complex Doped Host-Guest Film

PC Department Seminar
Date: Aug 12, 2022
Time: 11:00 AM (Local Time Germany)
Speaker: Ms. Shiori Miyazaki
Kyushu University, Japan
Location: Building G
Room: Seminar Room 2.06
Host: S. Maehrlein & A. Shiotari

Trivalent europium (Eu(III)) complexes are expected to be used as light-emitting materials such as organic light emitting diodes (OLEDs) because of their high color purity. The complexes are sensitized by the antenna effect, utilizing energy transfer from antenna ligands to a metal center. In the emitting layer of OLEDs, guest emitters are doped in host molecules, and intermolecular energy transfer also occurs.

To apply the complexes for OLEDs, elucidation of the energy transfer dynamics in the host-guest films is important. However, there are no design strategies except for energy matching of their lowest excited states. There are few direct observations of inter- and intra-molecular energy transfer processes in host and guest systems [1,2]. Here, we demonstrate a solution-processed system comprising a triazine-based host material and Eu(hfa)₃(TPPO)₂ (hfa: hexafluoroacetylacetonato, TPPO: triphenylphosphine oxide) shows drastically improved total luminescence intensity by one order of magnitude compared to conventional luminescent complexes. Time-resolved spectroscopies uncovered that energy transfer processes after photoexcitation of the triazine molecules take place via triplet states over several molecules with nearly unity efficiency.

[1] S. Miyazaki, K. Miyata, H. Sakamoto, F. Suzue, Y. Kitagawa, Y. Hasegawa, K. Onda, J. Phys. Chem. A 124, 6601-6606 (2020).
[2] M. W. Mara, D. S. Tatum, A. March, G. Doumy, E. G. Moore, K. N. Raymond, J. Am. Chem. Soc. 141, 11071-11081 (2019).