Regensburg 2002 – scientific programme
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SYOH: Organische Halbleiter
SYOH 7: Poster
SYOH 7.9: Poster
Monday, March 11, 2002, 18:00–21:00, C
Optical properties of thin tetracene films — •Michael Voigt1, Andreas Volz1, Andreas Langner1, Moritz Sokolowski1, Peter Schouwink2, John Lupton2 und Rainer Mahrt3 — 1Institut für Physikalische und Theoretische Chemie, Universität Bonn — 2MPI für Polymerforschung, Mainz — 3IBM Research, Zurich Research Laboratory
We report cw and time resolved optical data of crystalline tetracene thin films grown by vacuum sublimation onto a liquid substrate, ITO-glass and HOPG measured at 4 K to 300 K. The absorption spectra show a small continuous redshift of about 150 cm−1 with decreasing temperature. Additional absorption peaks seen below 240 K are explained by a structural phase transition. The luminescence spectra indicate a second phase transition at 70 K. The (0-0)-transition is found at 18.650 cm−1 (in luminescence) in agreement with spectra of free standing tetracene crystals. Additional trap emission (2.500 cm−1 below (0-0)) is traced back to structural defects in the tetracene films, and is correlated with the density of grain boundaries in the films.