Credit: © 2008 AIP

Conventional photovoltaics are made of inorganic semiconductors, such as silicon, with the electrical connections usually formed using indium tin oxide (ITO). However, increasing demand for indium for other industrial applications, such as flat panel displays, has led to concerns about rising costs and depletion of natural resources. Currently, despite the potential of organic materials as inexpensive alternatives for manufacturing solar cells, cell performance is limited due to the diffusion of indium from the ITO layer into the active layers of the solar cell.

Now, Jao van de Lagemaat and colleagues of the National Renewable Energy Laboratory and the University of Colorado1 have reported enhanced photoconversion in organic solar cells with silver front electrodes containing a random array of nanoholes. Notably, a 30-nm-thick silver film with 92-nm-diameter holes was 50% more efficient in converting transmitted light to an electric current compared with the ITO reference cell.

The authors suggest that this remarkable improvement in performance is the result of surface plasmons, which are light waves that are trapped on the metal surface owing to their interaction with free electrons in the film. The trapped light has more time to interact with the active layer of the solar cell, thereby improving cell performance.