Hanergy to make GaAs solar cells in Wuhan

20 Apr 2015

Investment in a 10 MW production facility follows acquisition of Californian start-up Alta Devices.

Thin-film GaAs

The Chinese solar giant Hanergy says it will invest in a 10 MW production facility to make thin-film gallium arsenide (GaAs) solar cells in Wuhan – home to the country’s most significant concentration of optics-related expertise.

The move, which will create the world’s only large-scale facility for making solar cells based on GaAs material that is not for space or concentrated PV applications, follows Hanergy’s acquisition of the Californian spin-out firm Alta Devices in August 2014. Alta has been developing the technology since being co-founded by Caltech’s Harry Atwater and Berkeley’s Eli Yablonovitch back in 2008.

According to a release from Hanergy, the first phase of the project will see a 3 MW production line established. The company also plans to set up a research and development center, and says that it has agreed a deal with the Huangpi District Government to both construct factory buildings that Hanergy will lease, and to promote the firm’s solar products in the local market.

The plan is to install 100,000 sets of thin-film arrays for households, and more than 1300 hectares of what it calls “photovoltaic agricultural greenhouses”, to reach 600 MW of installed solar capacity within two years after the agreement takes effect. “This will advance Wuhan’s efforts to develop green energy and build itself into a green, low-carbon city,” states the firm.

Higher efficiency; more power
While that largely relates to other thin-film PV technologies that Hanergy has acquired – deals over the past few years have seen it snap up the former Q-Cells division Solibro and US-based MiaSolé - the flexible GaAs technology developed by Alta has a much higher conversion efficiency, delivering twice the power of a conventional PV cell of similar size.

“The GaAs solar cells manufactured by Hanergy Thin Film, which boast not only high energy efficiency but also great flexibility, can be widely applied in many products from solar cars and phones to unmanned aircraft systems and IoT [Internet of Things] systems to extensive consumer electronics,” claims the Chinese firm.

The US National Renewable Energy Laboratory (NREL) currently lists Alta’s 28.8 per cent devices as the best-performing single-junction thin-film GaAs PV cells yet produced, while Alta announced in 2013 that operation with 30.8 per cent had been confirmed by NREL for its dual-junction designs without the need for concentration.

At the time, Alta CEO Chris Norris added that the company had set a target conversion efficiency of 38 per cent for those dual-junction cells, which use a layer of InGaP semiconductor material on top of the GaAs absorber layer in the base cell.

Fluorescence effects
That kind of high-efficiency, multi-junction technology has only previously been used in space applications to power satellites, and in concentrated photovoltaics (CPV) systems for terrestrial applications – but has largely proved to be too expensive for the latter, with CPV companies struggling in recent years against sharp falls in the cost of rival silicon PV technology.

Back in 2011, Alta told optics.org that fluorescence was the key to achieving such high conversion efficiencies in its GaAs thin films.

“Efficient light emission, both internal to the cell, and to the external world, is an indication of high carrier density, large quasi-fermi level splitting, and therefore the high open-circuit voltage,” the firm said, with co-founder Yablonovitch adding: “Counter-intuitively, efficient light emission is the key for these high efficiencies.”

The novel production process being developed by Alta also allows GaAs wafer substrates to be recycled and reprocessed, helping to cut the cost of what has traditionally been regarded as an exotic and expensive technology.

Investors certainly appeared to have bought into those claims and the Atwater group’s scientific pedigree, with the start-up company reportedly raising upwards of $120 million in venture funding by 2011.

Exactly how much of that investment was recouped in the Hanergy acquisition is not clear, but the move to scale production indicates that the Alta-developed technology certainly has a future – possibly outside of conventional solar deployments. The Chinese company says that it wants to target mobile and wearable technology applications, as well as the automotive sector.