a Nitride Thin Film semiconductor material technology that captures a wider spectrum of the sun's solar spectrum

A nitride thin film semiconductor material technology captures a wider spectrum of the sun's solar spectrum. (Credit: RoseStreet Labs Energy.)

A Phoenix company said it has created a hybrid solar cell that pairs a gallium-nitride thin film with typical silicon-based PV technology to produce a single unit it claims can achieve an efficiency of 25 percent to 30 percent.

RoseStreet Labs Energy announced the prototype cell Monday, and it expects to start commercial production late 2010, says Bob Forcier, CEO of RoseStreet. When those cells come off the first production line, they should be able to convert 25 percent to 30 percent of the sunlight that falls on them into electricity, he adds.

That kind of efficiency would be significantly greater than what the best silicon cells on the market can achieve today. Currently, the most efficient silicon cells for sale come from San Jose, Calif.-based SunPower, whose cells have 22.5 percent efficiency.

There are other types of cells that use alternative materials and perform much better than SunPower’s, but they also are much more expensive and are developed mostly for solar panels on satellites. The majority of the solar cells on the market today are made with silicon, and their efficiencies are typically in the mid-teens.

RoseStreet’s idea is that by adding a layer of gallium-nitride, PV panels can be tuned to make use of photons from a broader range of spectrum. “With gallium-nitride you can tune it for whatever [part of the spectrum] you want. It’s like a piano versus the ukulele – you get more notes with the piano,” Forcier says. “This technology allows silicon to be supercharged, like adding a big booster without a big cost penalty.”

Gallium-nitride is a common material for making LEDs, so sourcing it wouldn’t pose a challenge, he notes.

The company’s core technology came from Cornell University and the Lawrence Berkeley National Lab. RoseStreet’s chief technical officer is Wladek Walukiewicz, who also serves as a senior scientist at LBNL. Walukiewicz reached LBNL via the Warsaw Institute and at the Massachusetts Institute of Technology.

When the company announced its licensing agreement in 2005, it said the technology could lead to solar energy conversion efficiencies greater than 48 percent.

Although RoseStreet claims it will start production of the hybrid panels in late 2010, it could license its technology to other silicon makers that seek ways to significantly boost their products’ performance, Forcier says.

Interestingly, RoseStreet says its technology is not a one-trick pony. Two weeks ago, the company also announced that it had discovered a way to use a nitride thin film-based photoelectrochemical cell to produce hydrogen gas directly from sunlight.