Torben Menke

In-situ conductivity and Seebeck measurements of highly efficient n-dopants in fullerene C60

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.

Highly efficient semitransparent tandem organic solar cells with complementary absorber materials

We present highly efficient, semitransparent small molecule organic solar cells. The devices employ an indium tin oxide-free top contact, consisting of thin metal films. An additional organic layer is used to enhance light outcoupling. The solar cell incorporates two stacked subcells, each containing a donor:acceptor bulk heterojunction. The two subcells have complementary absorbers, with separate blue (C60), red (fluorinated zinc phthalocyanine), and green (dicyanovinyl oligothiophene derivative) absorbing molecules. A power conversion efficiency of 4.9 ± 0.2% is obtained for the device having an average transmission of 24% in the visible range.

Determining doping efficiency and mobility from conductivity and Seebeck data of n-doped C60 layers

In this work, we introduce models for deriving lower limits for the key parameters doping efficiency, charge carrier concentration, and charge carrier mobility from conductivity data of doped organic semiconductors. The models are applied to data of thin layers of Fullerene C60 n-doped by four different n-dopants. Combining these findings with thermoelectric Seebeck data, the energetic position of the transport level can be narrowed down and trends for the absolute values are derived.

Publisher’s Note: “Highly efficient semitransparent tandem organic solar cells with complementary absorber materials” [Appl. Phys. Lett. 99, 043301 (2011)]

Jan Meiss, Torben Menke, Karl Leo, Christian Uhrich, Wolf-Michael Gnehr et al. Citation: Appl. Phys. Lett. 100, 099901 (2012); doi: 10.1063/1.3679552 View online: http://dx.doi.org/10.1063/1.3679552 View Table of Contents: http://apl.aip.org/resource/1/APPLAB/v100/i9 Published by the AIP Publishing LLC.