Enhancing the performance of OPV cells with a new approach

It has been highlighted that harnessing the oscillation of electrons on conductor surfaces can effectively enhance the performance of organic photovoltaic cells.

A report authored by Anthony J. Morfa, Thomas H. Reilly III, Justin C. Johnson, and Jao van de Lagemaat,  referred to the trade-off between efficient light absorption and charge collection.

It mentioned that cells engineered to absorb as much light as possible exhibit decreased efficiency, because increased path lengths strongly increase energy losses by recombination of oppositely charged electrical carriers. Photovoltaics engineered to exhibit less recombination absorb less light.

A sweet spot can be found that has limited efficiency. To surpass this practical limit, new materials and approaches are needed.

A new way to increase solar-energy conversion is through surface plasmons, i.e., collective surface oscillations of conducting electrons in metal nanostructures that tend to trap optical waves near their surface. They enhance optical processes in their vicinity and are widely used in Raman spectroscopy, where enhancement factors can be many orders of magnitude.

It has been found that owing to the possibility of strong recombination occurring at metal surface, in contact with the active layer of a solar cell, attempts at this approach have not been very successful (except for some cases where they were used deliberately as recombination sites).

The authors claim that they have succeeded in circumventing these issues by employing buffer layers between the plasmonically active material and the active layer of the solar cell. They have also employed a hybrid approach, where plasmonic effects potentially enable third-generation solar-energy conversion.