Jonas Weickert

German

Organic solar cells are a promising new technology due to their easy processibility and potential low cost production. Power conversion efficiencies beyond 8 % have been realized with fully organic devices. The morphology of the active layer, where the light-to-charge conversion takes place, plays a key role in these devices and determines the efficiency. However, the morphology cannot be directly controlled. There are only limited studies on morphological effects on device physics and the "ideal" morphology is still unknown.

The introduction of nanostructured TiO₂ is an interesting approach to influence the morphology of the solar cells bulk heterojunction. Highly absorbing, hole conducting polymers can be infiltrated into dye-sensitized TiO₂, which also exhibits favorable electronic properties as electron collecting electrode. Additionally, confinement inside the nanostructures can enhance the hole mobility of the polymer. The heterojunction morphology can be directly controlled via shape and structure of the TiO₂ and the device absorption tuned by choosing an appropriate dye. Due to the combination of inorganic and organic active materials such devices are commonly called hybrid solar cells.

My research project focuses on fabrication of different TiO₂ morphologies and their application in hybrid solar cells. In-depth analysis of physical processes like charge separation, transport and recombination should provide insight into fundamental working principles of next-generation solar cells. Limitations should be identified to infer pathways towards highly efficient hybrid devices. Design rules concerning the ideal morphology should be revealed and might be applicable also for fully organic solar cells.

The work is carried out in collaboration with the groups of Prof. Christina Scheu (LMU Munich), Prof. Thomas Bein (LMU Munich) and Prof. Judith MacManus-Driscoll (University of Cambridge).

J. Weickert, F. Auras, T. Bein, L. Schmidt-Mende:
"Characterization of Interfacial Modifiers for Hybrid Solar Cells"
J. Phys. Chem. C, in press (2011)

M. Al-Hussein, H.C. Hesse, J. Weickert, L. Dössel, X. Feng, K. Müllen, L. Schmidt-Mende:
"Structural  Properties of the Active Layer of Discotic Hexabenzocoronene/Perylene Diimide Bulk-hetero Junction Photovoltaic Devices"
The Role of Alkyl Side Chain Length, Thin Solid Films, in press (2011)

H.C. Hesse, J. Weickert, C. Hundschell, X. Feng, K. Müllen, B. Nickel, A. J. Mozer, L. Schmidt-Mende:
"Perylene sensitization of fullerenes for improved performance in organic photovoltaics"
Adv. Energ. Mater., DOI: 10.1002/aenm.201100211 (2011)

J. Weickert, R. B. Dunbar, H. C. Hesse, W. Wiedemann, L. Schmidt-Mende:
"Nanostructured organic and hybrid solar cells"
Adv. Mater. 23 (16) 1810-1828 (2011)
DOI: 10.1002/adma.201003991

J. Weickert, C. Palumbiny, M. Nedelcu, T. Bein, L. Schmidt-Mende:
"Controlled growth of TiO2 nanotubes on conducting glass"
Chem. Mater. 23 (2) (2011), 155-162

J. Weickert, H. Sun, C. Palumbiny, H. C. Hesse, L. Schmidt-Mende:
"Spray-deposited PEDOT:PSS for inverted organic solar cells"
Sol. Energ. Mat. Sol. Cells 94 2371 (2010)

H.C. Hesse, J. Weickert, M. Al-Hussein, L. Dössel, X. Feng, K. Müllen, L. Schmidt-Mende:
"Discotic materials for organic solar cells: influence of chemical structure on assembly and performance"
Sol. Energ. Mat. Sol. Cells 94 560 (2010)