Looking deeply into polymer solar cells( Researchers from the Eindhoven Unive...)

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 them important new insights in the nanoscale structure of polymer solar cells and its effect on the performance. The findings were published online in Nature Materials on Sunday 13 September.

The investigations shed new light on the operational principles 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. Added to that, 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 these 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 degree of mixing of the two materials is essential for its efficiency. Intimate mixing enhances the area of the interface where charges are formed but at the same time obstructs charge transport because it leads to long and winding roads for the charges to travel. Larger domains do exactly the opposite. The vastly different chemical nature of polymers and metal oxides generally makes it very difficult to control the nanoscale structure. The Eindhoven researchers have been able to largely circumvent this problem by using 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.

Nanoscale mixing
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