Theoretically, the maximum efficiency of the highest-grade crystalline silicon solar cells is approximately 30 percent, because much of the sunlight that hits a solar cell is lost as heat. In practice, however, the most efficient solar cells on the market today operate at about 23 percent efficiency – that is, they convert about 23 percent of the energy hitting the cell into electricty. But Solar3D, a Santa Barbara-based solar energy technology startup, claims to be developing a breakthrough silicon solar cell technology that, according to preliminary tests, is capable of achieving an efficiency of 25.47 percent.
The company’s design concept for a three-dimensional solar cell utilizes light management techniques used in the fiber optics industry. Instead of allowing sunlight to bounce off the surface, Solar3D uses a top light-collecting layer, made of silicon dioxide or another similar material. This material, like a similar material being developed on a nano-scale at Northwestern University, does not absorb sunlight itself; instead, it guides it into three-dimensional micro-photovoltaic structures, each a few micrometers wide.
From here, the technology works like a funnel trapping sunlight, giving the photovoltaic material more time to convert it into electricity. Instead of passing through the photovoltaic material just once, the photons “bounce around” until nearly all of them are converted into electricity. Further efficiency improvements are achieved by running the electrical contacts under the light collectors, rather than across the top of the cell, like most photovoltaic cells. This prevents the wires from shading the cells, blocking the absorption of sunlight.