Solar PV tech eliminates rare elements

Quantum Solar Power is developing a solar cell technology that it says will eliminate the need for rare elements in the manufacture of thin-film photovoltaics.

February 16, 2011   by PLANT STAFF

Diagram of Quantum’s NGD technology. It replaces the thick semiconductor layers in conventional PV as the primary absorber of photons.

Diagram: Quantum

SANTA FE, NM: Quantum Solar Power Corp. is developing a solar cell technology that it says will eliminate the need for rare elements in the manufacture of thin-film photovoltaics.

The solar power technology developer based in Santa Fe, NM said its patent-pending Next Generation Device (NGD) technology will provide high-efficiency solar cells Next Generation Device priced competitively with coal generated electricity, without the use of rare elements.

Thin-film photovoltaics (PVs), which use nanometre-thin layers of material deposited on a substrate, are less efficient than silicon PVs, but are cheaper to manufacture and their use is growing.

Conventional thin-film devices are based on CdTe (cadmium telluride) and CIGS (copper indium gallium selenide) technologies. However, Quantum said growth to meet expected demand may be limited by the devices’ use of rare elements idium, tellurium and gallium. All are scarce globally, used in other high-production electronics such as flat screen TVs, and prices are escalating.

With conventional thin-film PVs, photons in sunlight pass through the glass coating, past the antireflective barrier and are absorbed by the semiconductor layer. Positive and negative charges are sent to opposite contacts by the junction, which leads to current flow in the circuit. The more light, the greater the flow of the current. In combination with the voltage output, this determines the power produced by a solar cell.

But Quantum contends the main limitation of this technology is the light-absorbing semiconductor that needs to be high quality for the device to operate efficiently, and thick enough to absorb all the light, which adds to the cost. Other impediments are the potential for material shortages and escalating costs of rare elements. Indium was $285 per kilogram in January 2009, now it’s $530; tellurium was $150 per kg in January 2010, now it’s $295; and gallium was $450 last year, now it’s $750.

Current global electrical consumption is 10 terawatts (10 trillion watts). Quantum says if thin-film PV solar power is to replace fossil fuel generated power, it must be scalable to this level of production.

Quantum doesn’t offer a lot of detail about its technology, except that it uses abundant, readily-available materials; it has a semiconductor-free absorber combined with a barrier that effects the separation process; and a patent-pending charge separation system provides broadband response DC current output.

The NGD technology is expected to produce devices with power conversion efficiencies above 20% while maintaining low production costs. As its research continues, Quantum’s goal is to break down the competitive barrier between solar power and fossil fuels.

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