Three-dimensional design promotes solar cell efficiency

Santa Barbara, Calif., Has a company called Solar3D that plans to build a silicon solar cell that is more efficient than a conventional battery because it uses photovoltaic-coated fiber technology Of the trap concept. The company claims that its three-dimensional design can condense light into the silicon to be captured, giving the material more time to convert light into electrical energy.

Silicon has a theoretical maximum photoelectric conversion efficiency of 29%, but today the market of solar panels, efficiency is only 15% to 18%. "The 260-watt standard PV panel weighs in that it will be close to the theoretical efficiency of silicon," says Jim Nelson, chief executive of the company. "We can not reach 29 percent, People can use silicon to reach that high, but we want to be as close as possible. "

Solar 3D's design will overcome the two factors that reduce the efficiency of solar cells. First, 30% of the light that is directed to a solar panel is reflected and lost. Second, many of the electrons that are generated when light is applied to the silicon are reabsorbed by the material before reaching the peripheral circuit.

Nelson said the new design had trenches on top of the light collection layer, made of silicon dioxide or other similar materials; these trenches can guide the light down, helping to eliminate reflections. The lower layer is a three-dimensional array of structures each of several microns wide, trapped by a waveguide used in the analog fiber. The fiber has two cylindrical layers with different refractive indices, which continuously reflect light back into the core. Nelson said that this three-dimensional structure will allow light to bounce around until the photon produces as much electrons. "We also make the contacts very close to where this happens, so that the electrons do not have to move very far," he says.

There are also many other concepts of trapping. Another way to borrow fiber technology, is the fiber-optic solar cells, Georgia Tech (Georgia Tech) researchers have made, is dye-sensitized solar cell wound optical fiber. However, Nielsen said that the Solar 3D company's batteries are using the traditional silicon material, so their preparation can use existing production equipment, can also be put into the existing module.

Solar 3D is at a very early stage, when it begins, as venture capitalists dare not invest in solar technology because of the high start-up costs. But the company does not seek venture capital. Instead, its funds come from private investors, including Nelson, who has a financial background, but has a passion for renewable energy. Analysts said the company's success will depend on whether its manufacturing costs can win over traditional crystalline silicon technology. "It's very difficult for emerging technologies to gain a foothold in the market," says Matthew Feinstein, an analyst at Lux Research. "Banks' discountability is often a major problem because these technologies do not have reliable track records."

These technologies, like Solar 3D, are expected to be more efficient because they will make solar power cheaper, says Georgina Benedetti, who is a Frost & Sullivan (Frost & Sullivan) analyst. However, she said, "the industry's main challenge is the competition from the Chinese manufacturing industry." Chinese-made solar panels cheaper, coupled with cost control troubles, leading to Solinndra (Solyndra) , A solar panel manufacturer in Fremont, Calif., Recently declared bankruptcy and was previously backed by a US Department of Energy loan guarantee.