Advanced Functional Materials and Devices (AFMD) Group

Abstract:

2-(2-Methoxyphenyl)-1,3-dimethyl-1H-benzoimidazol-3-ium iodide (o-MeO-DMBI-I) was synthesized and employed as a strong n-type dopant for fullerene C(60), a well-known n-channel semiconductor. The coevaporated thin films showed a maximum conductivity of 5.5 S/cm at a doping concentration of 8.0 wt% (14 mol%), which is the highest value reported to date for molecular n-type conductors. o-MeO-DMBI-I can be stored and handled in air for extended periods without degradation and is thus promising for various organic electronic devices.

Abstract:

We present two organic dimetal complexes Cr2(hpp)4 and W2(hpp)4 as n-dopants investigated in the model system of fullerene C60 for the application in organic electronic devices. Conductivity and Seebeck measurements on doped layers are carried out in vacuum at different doping concentrations and various substrate temperatures to compare the two dopants. Very high conductivities of up to 4 S/cm are achieved for both organic dopants. The thermal activation energy of the conductivity as well as the measured Seebeck coefficient are found to decrease with increasing doping concentration, indicating a shift of the Fermi level towards the electron transport level of the n-doped C60. © 2012 American Institute of Physics.

Abstract:

X-ray investigations on single crystals of a series of terminally dicyanovinyl-substituted quaterthiophenes and co-evaporated blend layers with C(60) give insight into molecular packing behavior and morphology, which are crucial parameters in the field of organic electronics. Structural characteristics on various levels and length scales are correlated with the photovoltaic performance of bulk heterojunction small-molecule organic solar cells.