Solar start-up squeezes more juice from silicon cells

1366 Technologies, a spinoff from the Massachusetts Institute of Technology, says it can produce a very efficient solar cell from silicon which will be in the market in two years.

The Lexington, Mass.-based company on Monday plans to disclose the details of its Self-Aligned Cell (SAC) architecture, a set of technologies it has developed to convert 18 percent of sunlight to electricity with polysilicon, the most common solar cell material. Engineers forecast that they will be able to hit 19 percent efficiency in the next nine months without adding significant cost to existing processes, said Ely Sachs, chief technology officer.

In addition, the company expects to announce in coming weeks that a solar manufacturer plans to purchase the machinery 1366 Technologies has developed for making the cells.

The announcement is a validation of 1366 Technologies' technical approach of making incremental improvements to well-established silicon solar cells, rather than seeking out new photovoltaic materials as many other solar start-ups have.

But the company, started in early 2008, has had to shift its business strategy from making solar panels themselves to selling equipment to other manufacturers. The poor financing environment and the intense price pressure on panel makers prompted the company to change course, Sachs said.

"This is a strategic change. We realized that we have very deep, unusually deep, competency in production equipment design," said Sachs. "Also, this is well-suited to doing in the U.S. whereas solar cell making is going to be a harder game to play in the U.S."

The long-term goal is sell to thousands of machines capable of producing more efficient cells to photovoltaic suppliers, he added. With the improvements in cell efficiency, the end product--solar panels--can be cheaper than electricity made from natural gas in the next few years and ultimately coal, he said.

Because of the daunting financing challenges in energy, other green-tech companies, including solar thermal start-up Ausra, have had to shift strategies in an effort to get their technologies to market more quickly.

Trapping more light
There are already silicon solar cells that get higher efficiency than what 1366 Technologies says it can do. SunPower has been selling panels at over 20 percent efficiency for a few years. Meanwhile, Georgia Tech spinoff Suniva late last month said that it could convert more than 18 percent of sunlight to electricity on monocrystalline silicon cells and Chinese provider Suntech has a technology called Pluto which boasts improvements in that range.

But the efficiency rating for the majority of commercially available silicon solar cells is in the 15 percent range. Panels using cells made from alternative materials, such as a combination of copper, indium, gallium, and selenide (CIGS), are lower efficiency--about 9 percent or 10 percent--but are cheaper to produce.

The technologies that 1366 has developed are significantbecause they can be added onto to existing processes and are complementary with each other, say company executives. Some are related to trapping more light on the solar cell while another uses a different method for wiring cells together.

One technique is to create a three-dimensional pattern, or topography, on the surface on the cells that keeps light on the cell long enough so that more can be absorbed, Sachs explained.

The other process, called surface metallization, shrinks the size of the wires, or "fingers," on the front of cells. Instead of using the typical screen printing method, 1366 Technologies engineers have built a machine that's able to make the silver wires using electroplating and to place them on the cell. Shrinking the fingers from the typical 120 microns to 30 microns reduces shading on the cell and allows manufacturers to put more fingers on a cell to improve performance, Sachs said. The company also expects to be able to replace silver with copper to reduce cost, he added.

"These are three manufacturing technologies and they play together so you can use them all and get the cumulative benefits but you can use just one," he said.

1366 Technologies has already licensed another light-trapping technology where a grooved surface on the back of solar cells reflects light back onto the surface. Earlier this year, the company received a research grant from the National Renewable Energy Laboratory which it is still participating in.