US scientists produce plastic solar cells

Solar cells might one day be produced by the roll, as cheaply and easily as wallpaper as scientists in Arizona are using screen-printing, a technique developed for patterning fabrics, to produce plastic solar cells, reports Nature Science.

The organic cells manufactured by researcher Ghassan Jabbour and his colleagues at the University of Arizona in Tucson have about a quarter of the efficiency of commercial silicon devices, which turn 10-20% of light energy into electricity, but being cheap to produce, can make up in quantity what they lack in quality.

The researchers print very flat, very thin cells onto glass in a similar way to conventional screen-printing. First, the glass is coated with a transparent, electrically conducting material that acts as one of the solar cell’s electrodes. On top of this, a thin film of a polymer is laid, which helps to gather current from the photovoltaic material and finally the researchers deposit a blend of two organic compounds that convert light into electricity.

One, a carbon-based molecule called a fullerene, produces charged particles that carry an electrical current when light shines onto the molecules. The other, a polymer, ferries the current to electrodes on the top and bottom of the cell.

Under blue light, these screen-printed solar cells have an efficiency of 4.3%. They are probably less efficient for white sunlight, so there is work to be done before the devices are good enough for commercial use, say the researchers.

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