RoseStreet Labs develops breakthrough multiband solar cell technology

This story is specifically meant for those either connected with or interested in the global solar PV industry. And, it concerns a wonderful technological breakthrough!

Now, I'm not sure how many of you heard this story -- late last month, scientists at Phoenix, Arizona, USA, based RoseStreet Labs Energy Inc. (RSLE), chairman and CEO, Bob Forcier, announced a breakthrough multiband solar cell technology.

A bit about the company: RoseStreet Labs has ventured into the semiconductor, renewable energy and life science markets with strategic investments, intellectual property development, three joint ventures and a successful spin out in personal health technology. RSLE's first commercialization business, FlipChip International (FCI), experienced double digit growth annually and opened its FCMS joint venture in Shanghai, China.

Naturally, this prompted me to get in touch with Bob Forcier at RoseStreet Labs, with the help of Dawn Cuevas, office manager - RSL/FCI.

But first, the breakthough achievement!

RoseStreet Labs announced a breakthrough lab demo of the first known multiband photovoltaic device featuring three distinct light absorption regions integrated into a single layer thin film device.

This breakthrough is based on RSLE's IBand technology and is the first known intermediate band solar cell reduced to practice in a laboratory demonstration. This technology illustrates great promise for high efficiency thin film solar efficiencies above 35 percent by potentially capturing the full spectrum of the sun's spectrum.

According to the company, the intermediate band solar cell developed by RSLE is a thin film technology based on the discovery of highly mismatched alloys. The simple and elegant three bandgaps, one junction device has the potential of significantly improved solar light absorption and higher power output than the III-V triple junction compound semiconductor devices that presently hold the world record for solar efficiency.

Three cells for the cost of one cell!
I quizzed Bob Forcier about the multiband solar cell technology. He said, "It involves a less complex approach that replaces the currently used triple junction approaches for full spectrum high efficiency capture."

So, what can RSLE's IBand technology do for solar? Well, once commercialized, the IBand technology has the potential to change the game in +30 percent efficient cells, claimed Forcier.

"Basically, going from complex and expensive triple junction devices to simple, single junction thin film devices, which are inherently much more cost efficient," he added. Very importantly, solar PV players can use the IBand technology in two formats -- terrestrial flat panels and terrestrial CPV formats, respectively.

Currently, all of this is said to be achieved in a complex and expensive technology in which several solar cells with different band gaps are connected in series. A much simpler approach in which a single semiconductor has several different gaps sensitive to different parts of the solar spectrum has been proposed but never realized. "Simply put, it is like getting three cells for the cost of one cell," said Forcier.

RLSE's intermediate band solar cell is a prototype cell that demonstrates the technology can work. "Its efficiency is low since the technology is quite new and we are still developing the technology," he noted.

On the technology promising high efficiency thin film solar efficiencies above 35 percent, Forcier clarified: "We are presently below 35 percent. However, we are testing our prototype cell with both single sun and concentrated sun illuminations. The 35 percent comes from modelling of the band structure with realistically achievable material parameters."

RoseStreet is anticipating and planning for IBand technology production in 2013. This is a reasonable amount of time for a disruptive technology like IBand, Forcier said.

A new class of semiconductor devices for photovoltaic conversion and other advanced semiconductor applications will also likely get opened up. These would mostly be in sensors and high performance switching, such as power amplifiers for wireless.