8 June 2012

Alta discloses technologies behind flexible GaAs solar cells for adaptable form factors

At the 38th IEEE Photovoltaics Specialists Conference (PVSC38) in Austin, TX (5-7 June), technology manager Dr Laila Mattos of Alta Devices in Sunnyvale, CA, USA presented details of key technologies that enabled it to reach a new record of 23.5% energy conversion efficiency for single-junction gallium arsenide (GaAs) solar modules, as confirmed by the US National Renewable Energy Laboratory (NREL) and announced in February.

Founded in 2007, Alta is a development-stage company focused on improving the production economics of high-efficiency solar PV applications, as well as on making breakthroughs in both manufacturing and form factor. So far the firm has received $72m in venture capital funding from investors including August Capital, Kleiner Perkins Caufield & Byers, Crosslink Capital, DAG Ventures, New Enterprise Associates (NEA), Presidio Ventures, Technology Partners, Dow Chemical, and Alberta Investment Management Corporation (AIMCo).

At PVSC, Alta described how its thin-film solar cells are interconnected into flexible sheets, creating what is claimed to be a new class of solar material. The material can be formed into different shapes and sizes, enabling new applications.

“Up until now, the applications of relatively high-efficiency solar have been constrained to those that utilize large and heavy glass plates,” says president & CEO Chris Norris. “But the technology being disclosed this week has the potential to change both the applications and economics of solar,” he reckons.

Due to the high efficiency combined with its thin and flexible nature, Alta’s solar material can be used differently from those that have been available, allowing meaningful power production anywhere the sun is shining, it is claimed. It can be deployed in many applications including: electric vehicles, aircraft and unmanned drones, portable power, roof tiles and other building-integrated uses. Because of the characteristics of the technology, the high cost of an entire solar energy system is reduced, the firm adds.

“When you are able to use solar in nearly any form, the applications broaden and the system complexity and cost are dramatically reduced and, ultimately, both the economic returns and human benefits increase,” says Norris.

In addition to underscoring previously disclosed techniques for overcoming the cost and complexity of using GaAs, Mattos’ presentation explained how Alta was able to maintain conversion efficiency while creating flexible sheets that can be of nearly any size. Specifically, she revealed that Alta's solar cells are self-interconnected in a way that maximizes the light captured by the thin, flexible sheets.

“Traditionally, when solar cells are interconnected to form a module, conversion efficiency is compromised because active solar material is covered with metal busbars and wires, preventing some of the light from entering the cells,” Mattos explains. “In addition, gaps between cells create areas of the module that are not able to convert incident light to electrical energy,” she adds.

“The key to improving solar performance at the module level is to avoid these problems,” continues Mattos. “Enabled by our cell flexibility, we use a self-interconnected technology that eliminates the wires, thus maximizing the cells’ exposure to incident light. The self-interconnected cells form a flexible sheet with no gaps and that can be of any size or aspect ratio.”

Construction of Alta’s pilot manufacturing facility is underway, with expectations of material available by the beginning of 2013. “We take every step of our business systematically and don’t underestimate the challenges,” concludes Norris.

See related items:

Alta’s single-junction GaAs solar panel verified by NREL as 23.5% efficient

Tags: Alta Devices GaAs PV

Visit: www.altadevices.com