Dresden 2006 – wissenschaftliches Programm
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CPP: Chemische Physik und Polymerphysik
CPP 21: SYMPOSIUM Functional Organic Thin Films II
CPP 21.7: Vortrag
Donnerstag, 30. März 2006, 16:00–16:15, ZEU Lich
How single conjugated polymer molecules respond to electric fields — •F. Schindler1, J. M. Lupton1, M. J. Walter1, U. Scherf2, and J. Feldmann1 — 1Photonics and Optoelectronics Group, Physics Department, LMU München — 2FB Chemie, Universität Wuppertal
For a microscopic understanding of the operation principle of optoelectronic devices based on organic thin films, such as polymeric light-emitting diodes, it is imperative to investigate the role of external electric fields (EFs) on the single molecule level. Single molecule fluorescence spectroscopy is a versatile tool for studying the intrinsic properties of individual chromophores which constitute the photophysical entity of a conjugated polymer (CP) molecule [1]. Here, we present the first report on how EFs influence the emission of single chromophores at low temperatures. Surprisingly, we observe a linear Stark effect which originates from a permanent polarisation of the π-electron system [2]. This can be thought of in terms of an effective dipole, which is averaged out in the ensemble but nevertheless sensitively controls bulk effects. The effective dipole orientation with respect to the backbone is identified for different CPs and provides direct insight into the intrinsic internal EFs acting on the single chromophore. These fields lead to charge conjugation symmetry breaking of the π-electron system and naturally bear substantial implications for the use of conjugated polymers in functional organic thin films.
[1] F. Schindler et al., PNAS 101, 14695 (2004)
[2] F. Schindler et al., Nature Mat. (in press)