Solar Cell Efficiency Theoretically Doubled

Solar cells are only capable of converting less than one-third of the solar energy they collect into electricity.

Now Sharp Electronics has come up with a prototype based on "exotic physics" that more than doubles that efficiency.

If such a device can be brought to market, solar power could become widely economical.

To accomplish this new efficiency, the Sharp researchers had to solve the problem of waste heat. When sunlight strikes conventional solar cells, it generates high-energy electrons, which lose most of their energy as waste heat within a few trillionths of a second.

Sharp constructed a device that isn't very practical because it's too thin to soak up much light and it works with only a single light wavelength. Still, it's the first device ever to corral these elusive electrons and increase the cell's voltage output. In theory, Sharp reports, efficiency could reach 60 percent, more than twice the efficiency of today's most efficient cells.

The technique used by the Sharp team is one of several that eventually could bring solar power generation fully into the mainstream by making it less expensive than using fossil fuels. That's because doubling a cell's efficiency would shrink the size of solar panels, making them far less expensive to install, a procedure that often is more expensive than the panels themselves.

Exotic physics, the key to the research, is all about fully understanding how certain materials behave and constructing them with pinpoint precision. The Sharp device relies on making extremely thin layers of a semiconductor made from gallium and arsenic. This creates a kind of shortcut for moving high-energy electrons.

Another, but very expensive, approach, according to the website Compound Semiconductor (CS), achieves high efficiency by assembling different kinds of solar cells in a stack array. Meanwhile, CS reports that researchers at the Massachusetts Institute of Technology are studying the behavior of electrons in organic materials in their search for more affordable ultra-efficient solar cells.

All these approaches are still in their early phases. And James Dimmock, the senior researcher on the Sharp team, says that for now, at least, the company's new technique will be limited to increasing the efficiency of conventional solar panels, not to create new devices altogether.