A copper oxide solar cells on top of regular silicon solar cells cold boost energy conversion up to 40% from 25% today

Researchers are currently developing the environment-friendly solar cells of the future, which will capture twice as much energy as the cells of today. The trick is to combine two different types of solar cells in order to utilize a much greater portion of the sunlight.

“These are going to be the world’s most efficient and environment-friendly solar cells. There are currently solar cells that are certainly just as efficient, but they are both expensive and toxic. Furthermore, the materials in our solar cells are readily available in large quantities on Earth. That is an important point,” says Professor Bengt Svensson of the Department of Physics at the University of Oslo (UiO) and Centre for Materials Science and Nanotechnology (SMN).

Ninety-nine per cent of today’s solar cells are made from silicon, which is one of the most common elements on Earth. Unfortunately, silicon solar cells only utilize 20 per cent of the sunlight. The world record is 25 per cent, but these solar cells are laced with rare materials that are also toxic. The theoretical limit is 30 per cent. The explanation for this limit is that silicon cells primarily capture the light waves from the red spectrum of sunlight. That means that most of the light waves remain unutilized.

The new solar cells will be composed of two energy-capturing layers. The first layer will still be composed of silicon cells.

“The red wavelengths of sunlight generate electricity in the silicon cells in a highly efficient manner. We’ve done a great deal of work with silicon, so there is only a little more to gain.”

The new trick is to add another layer on top of the silicon cells. This layer is composed of copper oxide and is supposed to capture the light waves from the blue spectrum of sunlight.

“We have managed to produce a copper oxide layer that captures three per cent of the energy from the sunlight. The world record is nine per cent. We are currently working intensely to increase that percentage to twenty per cent. The combination of silicon cells in the one layer and copper oxide cells in the other means that we’ll be able to absorb far more light and thereby reduce the energy loss. With this combination, we can utilize 35 to 40 per cent of the sunlight,” emphasizes Bengt Svensson.

There will also be other layers in the solar cell panel. On the back surface, a protective glass layer will be deposited, along with a metal layer that conducts the electricity out of the solar cell. The front side will have an antireflective coating, so that the light rays are captured rather than reflected away.

Many researchers and technology firms are working now on the new type of solar cells with silicon in the bottom layer and a layer of “more exotic materials” on top.

The Romanian solar cell company, Wattrom, intends to show that it is possible to manufacture the new solar cells.

“The technology is inexpensive, it can easily be scaled up to large volumes, and it’s not more expensive to produce solar cells out of copper oxide than out of silicon,” says Bengt Svensson.

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