13 April 2007

For all the sunlight they convert to energy, silicon solar panels are still costly, bulky, and brittle.

Now, a new kind of thin, flexible, film-like photovoltaic cell is about to go into commercial production for the first time.

The solar cells, coated with a common ingredient used in toothpaste and suntan lotion, will be four to five times cheaper than silicon. Manufactured with a process similar to inject printing, the cells will be able to produce electricity from direct sunlight as well as low-light and indoor lighting.

"Conventional silicon-based solar cells are more efficient in optimum conditions, but we win on the 24-hour cycle because our cells can use early morning light and work indoors. You can recycle energy from the electric lights in your building," said Clemens Betzel, president of G24 Innovations in Cardiff, U.K.

At the end of April, the factory will begin production of the cells — which were invented in 1988 by Michael Grätzel of the Federal Polytechnic School of Lausanne in Switzerland.

The company’s first application will come in the form of a cell phone charger. But the thin, flexible cells could eventually be installed across surfaces such as walls, counters and floors to power office and home electronics.

The so-called "dye-sensitized solar cells," also known as Grätzel cells, convert sunlight into energy similar to how leaves and plants do it through photosynthesis.

In leaves, chlorophyll molecules absorb sunlight and generate electric charges. Other mechanisms in the plant separate the positive and negative charges and conduct them to create energy.

Instead of chlorophyll, the Grätzel cells use titanium oxide to absorb the sunlight. The material is coated onto one of two conducting electrode layers, similar to foil. A gel-like electrolyte material is sandwiched between the two layers.