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SYOH: Organic and Hybrid Systems for Future Electronics
SYOH 3: Electronic Structure and Transport Properties
SYOH 3.2: Vortrag
Donnerstag, 11. März 2004, 16:15–16:30, H37
Dynamics of Hot Electrons in PTCDA Thin Films — •Steffen Berger, Alexander Mönnich, Jens Wüsten, Martin Aeschlimann, and Christiane Ziegler — University of Kaiserslautern, Department of Physics,
Charge carrier dynamics are of importance for many applications of organic semiconductors. We therefore studied the electron dynamics in 100 nm thin 3,4,9,10-perylene-tetracarboxylic dianhydride (PTCDA) films without and with dopants by means of time-resolved two-photon photoelectron spectroscopy (TR-2PPE) on a femtosecond scale.
As light source a titanium-sapphire laser system with a repetition rate of 80 MHz and a pulse length of 20 fs was used. Frequency doubling gives a photon energy of 3.1 eV, which allows to examine the life time of electrons in PTCDA with energies of 1.3-3.0 eV above the Fermi level.
By deposition of alkali-metals such as Na the conductivity of the n-type organic semiconductor 3,4,9,10-perylene-tetracarboxylic dianhydride (PTCDA) can be increased by several orders of magnitude. In TR-2PPE we observed an increase in the life time of electrons with energies >1.2 eV above EF after Na reaction. This can be explained by results from inverse photoemission spectroscopy which reveals that the density of states at 1.2 eV above EF is reduced by the same process, i.e. there are less unoccupied states in which the hot electrons can relax.