Mixing mismatched elements can enhance efficiency of solar cells

Researchers from the University of Michigan and Tyndall National Institute in Ireland have discovered new materials that could give birth to a new breed of highly efficient solar cells.

The research team, led by Rachel Goldman of the University of Michigan, is currently developing a unique class of materials called highly mismatched alloys to greatly enhance the efficiency of solar cells. They claimed that these materials can fully capture the sun’s rays, unlike traditional solar cells.
Conventional solar cells convert radiant energy from the sun into electricity by absorbing light. However, the sun gives out light at different wavelengths, each with different intensities of energy, and current solar cells only respond well to some wavelengths.

The cells only harness energy from the visible spectrum, holding 43 percent of the sun’s radiant energy. But the infrared portion of the range, which offers about 52 percent of solar energy, is often overlooked in solar panel production.

The most efficient solar cells are made of multiple materials that can capture a greater portion of the sunlight spectrum, and solar panel developers worldwide are seeking to develop the perfect solar cell that will make use of the sun’s infrared light.

The research team were very interested in using highly mismatched alloys for solar cells because its electrical and optical properties drastically change when exposed to certain elements.

In their experiments, the researchers made samples of gallium arsenide nitride, a highly mismatched alloy with nitrogen, to tap into the infrared radiation.

One of the biggest problems to get mismatched alloys out of the lab is that the materials do not naturally mix together with the elements that imbue them with special properties. However, the researchers used molecular beam epitaxy, which involves vaporizing pure samples of the mismatched elements and combining them in a vacuum, to coax the nitrogen to mix with their other elements.
If researchers can learn to control the formation of these clusters, they could build materials that are more efficient at converting light and heat into electricity, Ms. Goldman said.

A large amount of efficiency is possible if future solar panels could capture energy directly from the sun and indirectly from energy re-radiated all around by the ground and buildings.

"The availability of higher efficiency thermoelectrics would make it more practical to generate electricity from waste heat such as that produced in power plants and car engines," Ms. Goldman added.

The team’s research is funded by the National Science Foundation, the Science Foundation Ireland and the Center for Solar and Thermal Energy Conversion, an Energy Frontier Research Center financed by the United States Department of Energy.

Source:  EcoSeed ... article written by Oliver M. Bayani

Stanford Researchers Develop New Solar Energy Conversion Method

Researchers at Stanford University are working on a new way of converting solar energy. Their work may lead to technology could increase solar panel efficiency by up to 50 percent.

The new method is called PETE — photon enhanced thermionic emission — and may allow solar panels to harness the wasted heat in today’s generating process. Today’s conventional solar energy systems convert the sun’s energy into electricity by either electrical or thermal conversion. PETE, says lead research Nick Melosh, fuses the two conversion methods. Here’s how it works:

A main challenge posed by silicon-based solar panels is that efficiency decreases as ambient temperature goes up. Hot regions that have an abundance of direct sunlight — like parts of the American southwest — are great places to install these kinds of panels. But they could be greater still if there existed solar panels that performed well in high temperatures.

That’s exactly what the Stanford researchers are working on.

The metal Caesium (CS), pictured above, could be the key in increasing the efficiency rate of solar cells by more than 50 percent.

When only silicon is used, just a portion of the light spectrum is actually used to generate electricity. The rest of the energy is wasted because of the decline in efficiency rate at high temperatures.

By adding a thin layer of caesium, researchers enable the silicon to produce electricity from both light and heat. So as conventional silicon-based semiconductors decline at 100 degrees Celsius, the PETE method doesn’t even hit its top efficiency rate until 200 degrees Celsius.

The next step for the the Stanford team is to design a prototype that can be added on to existing systems. We’ll keep you posted.

Source:  getsolar.com