YOU want efficient solar power, Victor Klimov has a deal for you. Give him one photon of sunlight, and he'll give you two electrons' worth of electricity.

Not impressed? You should be. In all solar cells now in use - in everything from satellites to pocket calculators - each incoming photon contributes at most one energised electron to the electric current it generates. Now Klimov, a physicist at Los Alamos National Laboratory in New Mexico, has broken through this barrier. He has shown that by shrinking the elements of a solar cell down to a few nanometres, or millionths of a millimetre, each captured photon can be made to generate not one, but two or even more charge carriers.

Producing this multiplicity of electrons - an achievement that has been replicated by a group at the National Renewable Energy Laboratory (NREL) in Golden, Colorado - is a remarkable piece of physics. If the effect can be harnessed, it could change the whole energy debate by making solar power much more efficient and economical. While there are many ongoing efforts to improve solar efficiency - by concentrating sunlight, for example, or by making it easier for electrons to move around within a cell - the new approach is unique in that it gets to the very root of the process and also complements other methods.

For decades, photovoltaics have been stranded on the effete fringe of energy technologies - ideal for niche applications such as satellites, but not economically competitive here on Earth. Made from semiconducting materials, most often silicon, solar cells convert a dismayingly small fraction of the sun's energy into electricity. Radically improving efficiency could give solar energy a boost at a time when it is sorely needed and funding decisions hang in the balance. "If this could be translated into a robust system that could generate multiple carriers, it could be revolutionary," says Eric Rohlfing, acting director of the chemical sciences, geosciences and biosciences division in the Office of Basic Energy Sciences at the US Department of Energy.

If each photon can generate multiple charge carriers, the overall power efficiency of solar cells could be dramatically increased. The world record for a ground-based cell is 24.7 per cent, achieved by a device made in Australia at the University of New South Wales. Klimov predicts that the multiple-carrier generation could one day yield a cell with double that efficiency, approaching 50 per cent. Ellingson is slightly more conservative, but he still projects efficiencies around 45 per cent. With more work, the chips cranking out extra electrons in New Mexico and Colorado could one day bring a bright solar future for us all.