Berlin 2012 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 24: Poster: Organic Semiconductors
CPP 24.30: Poster
Mittwoch, 28. März 2012, 11:00–13:00, Poster A
Triplet excimer emission in CBP-derivatives — •Alexander Rudnick1, Sebastian Hoffmann1, Pamela Schrögel2, Peter Strohriegel2, and Anna Köhler1 — 1Uni Bayreuth, Experimentalphysik II — 2Uni Bayreuth, Makromolekulare Chemie I
Carbazole-biphenyl-derivatives (CBP) are widely used as host matrix materials for efficient phosphorescent organic light-emitting diodes (OLEDs). For blue phosphorescence, a key requirement is a high energy of the triplet excited state, and no other decay channels. Here we have investigated the electronic and optical properties of two series of CBP derivatives using time-resolved fluorescence and phosphorescence measurements in combination with density functional calculations. We show that such materials form sandwich-type triplet excimer states at 2.5 eV that compete with the monomer triplet state at 3.0 eV and that are detrimental to OLED performance.[1] The broad excimer emission can be suppressed using three approaches, (i) by adding sterically demanding outer groups, (ii) by enforcing torsion of the central biphenyl group and (iii) by changing the position where the pendant carbazole is attached to the biphenyl moiety from a para- to a meta-connection.[2,3]
[1]ST Hoffmann et al, J. Phys. Chem. B, 2011, 115, 414-421
[2]P. Schrögel et al, J. Mater. Chem., 2011, 21, 2266-2273
[3]P. Schrögel et al, Organic Electronics, 2011, 12, 2047-2055