About one quarter of the energy in sunlight is essentially lost on solar cells because they can’t convert light in the infrared spectrum into electricity. That has led to an active field of research in so-called black silicon, in which the surface of silicon solar cells is modified to absorb rather than reflect infrared light.

German research institute Fraunhofer says it has developed a way to double the efficiency of black silicon. If incorporated into existing photovoltaic manufacturing, the technique could improve silicon cell efficiency, which averages around 17 percent, by 1 percent.