More Efficient Solar Cells...

Science NOW - AAAS

Researchers have created a new type of solar cell that captures some of the excess energy in sunlight normally lost as heat. So far, the new solar cells still convert sunlight to electricity at an efficiency well below commercial solar cells. But if the process can be improved, it could help pave the way to a new generation of solar cells with higher efficiencies.

For most materials, the conversion of photons of sunlight to electricity is well understood. Photons of different colors have different amounts of energy. In the visible spectrum, reds and oranges have less energy, while blues, violets, and ultraviolet photons carry progressively more. When high-energy photons hit a semiconducting material in a solar cell, they give up this energy to the semiconductor's electrons, exciting them from a static position so that they are able to conduct. In many cases, high-energy photons—violets and ultraviolets—carry far more energy than is needed to give electrons the nudge to conduct. But this excess energy is lost as heat.

Science NOW: Solar Cells Capture Lost Energy