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Uli Lemmer
Project Leader
Prof. Dr. Uli Lemmer

Karlsruher Institut für Technologie (KIT)
Lichttechnisches Institut
Engesserstrasse 13

76131 Karlsruhe

+49 (0)721 608 42530

uli lemmer∂kit edu


F1: Solar Cells

Organic Solar Cells

Organic solar cells are photovoltaic devices that use the separation of photoexcited bound electron-hole pairs (excitons) at internal interfaces between two organic semiconducting materials on a nanometer scale. Among photovoltaic devices, organic solar cells have a huge potential for future sustainable electricity generation due to their simple and inexpensive roll-to-roll fabrication. With current record conversion efficiencies of about 8 %, organic solar cells are closing the gap with other 3rd generation solar-cell technologies. Further enhancement of this value is in the center of worldwide research activities.

Hybrid Solar Cells

Absorption of a photon creates an exciton which has to diffuse to the internal interface for dissociation into a carrier pair. Following absorption and dissociation the carriers have to be transported to the electrodes with resistivity and recombination losses as low as possible. Only so called bulk-heterojunction cells, consisting of partly segregated two-component materials, currently achieve high efficiency. All above-mentioned electronic processes are determined by the nanoscale morphology of these complex segregated systems.

Goals of the Project

Project F1 is concerned with substantially improving the performance and reducing the costs of organic solar cells by exploiting the possibilities to tailor organic and organic/inorganic materials on a nanometer scale.

Subproject F1.1 addresses new concepts for hybrid solar cells, F1.2 focuses on the electronic and morphological properties of organic and hybrid solar cells, and F1.3 on the synthesis of nanoscaled particles.

Visions and Perspectives

In F1 new concepts for organic and hybrid solar cells are studied, with special emphasis on the electrical and morphological properties, and the chemistry and preparation of alternate, nanoscale transparent conductive oxides (TCO) are evaluated. F1 has already developed highly conductive, organic composite electrodes and realized an all-solution-processed organic tandem solar cell. We intend to continue and strengthen these topics, by adding new questions to reflect recent and steer future developments.