Berlin 2012 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 99: Organic Semiconductors: Transport
HL 99.9: Vortrag
Freitag, 30. März 2012, 11:45–12:00, EW 203
Seebeck Measurements on Two Air-Stable n-Dopants for C60 — •Torben Menke1, Peng Wei2, Debdutta Ray1, Zhenan Bao2, Karl Leo1, and Moritz Riede1 — 1Institut für Angewandte Photophysik, TU Dresden, Germany — 2Department of Chemical Engineering, Stanford University, USA
Thin layers (30nm) of fullerene C60 are doped, using two different air-stable n-dopants with varying doping concentration. Conductivity and thermovoltage (Seebeck) measurements in vacuum are discussed and the influences of doping ratio and temperature are compared to investigate the nature of the doping process. The n-dopants investigated are the commonly used 3,6-bis(dimethylamino)acridine (acridine orange base, AOB) and a novel 1,3-dimethyl-2-phenyl-2,3-dihydro-1H-benzoimidazole derivate (R-DMBI). With increasing doping concentration the Seebeck coefficient is found to decrease, indicating a Fermi energy shift towards the transport state. For both dopants and different doping concentrations the energetic difference between the Fermi energy and the transport level is observed and compared to the thermal activation energy of the conductivity. Both energies show the same trend of a strong reduction with increasing doping concentration, confirming an increase of the free charge carrier density. Conductivity and Seebeck measurements are combined to estimate the mobility of the layers. These results show that R-DMBI is a promising and air-stable n-dopant for replacing AOB in the future.