Nanoscopic 3D images provide inside of a polymer solar cell

Technology.am (Sept. 14, 2009) — Researchers from the Eindhoven University of Technology and the University of Ulm have made the first high-resolution 3D images of the inside of a polymer solar cell. This gives new insights in the nanoscale structure of polymer solar cells.

These solar cells do not have the high efficiencies of their silicon counterparts yet. Polymer cells, however, can be printed in roll-to-roll processes, at very high speeds, which makes the technology potentially very cost-effective.

Polymer cells are flexible and lightweight, and therefore suitable to be used on vehicles or clothing or to be incorporated in the design of objects.

In the hybrid solar cells, a mixture of two different materials, a polymer and a metal oxide are used to create charges at their interface when the mixture is illuminated by the sun.

The Eindhoven researchers have used a precursor compound that mixes with the polymer and is only converted into the metal oxide after it is incorporated in the photoactive layer. This allows better mixing and enables extracting up to 50% of the absorbed photons as charges in an external circuit.

The 3-D nanoscopic morphology shows the image of a polymer-metal oxide solar cell. The team has been able to resolve the mixing with unprecedented detail on a nanoscale. From these images the researchers have been able to extract typical distances between the two components, relating to the efficiency of charge generation, and analyze the percolation pathways, that is, how much of each component is connected to the electrode. These quantitative analyses of the structure matched perfectly with the observed performance of the solar cells in sunlight.