Abundant zinc could replace rare earth staple in solar panels

London
Source:
This story is sourced from Flight International
Subscribe today »

Oxford University researchers may have cracked open a new route to exploiting solar power with the discovery of a low-cost alternative to indium, the scarce - and expensive - rare earth element that has been the key ingredient in photovoltaic panels for half a century.

The zinc-based transparent conductor is less efficient than indium tin oxide (ITO), but has a great advantage in manufacturing. While ITO has to be applied to its substrate material in a vacuum chamber, the Oxford team's silicon-doped zinc oxide is a liquid that can be sprayed on like paint, making it practical to apply on large and flexible surfaces - potentially including aircraft wings and fuselages.

Professor Peter Edwards, head of inorganic chemistry at Oxford and a fellow of St Catherine's College, says that while the zinc material is only about two-thirds as conductive as ITO, its optical transparency - one of ITO's most attractive characteristics - is about the same. As a consequence, he believes zinc could also replace ITO in touch screens and LCD displays.

Indium is scarce and expensive, and subject to price volatility. ITO commands more than 97% of the transparent conducting oxide market globally, but the price of indium is volatile and half the supply comes from China, which is cutting export limits.

Moreover, known indium reserves will only satisfy about 20 years' demand. Zinc, by contrast, is abundant.

The work of Edwards' group has been rewarded with the £25,000 ($39,000) Materials Science Venture Prize, given by the Worshipful Company of Armourers and Brasiers to encourage scientific entrepreneurship. The money will be used to demonstrate the material's suitability for use in solar panels, LCD displays and organic light-emitting diode (OLED) lighting.

Jamie Ferguson, of Oxford University's technology transfer company ISIS Innovation, describes the material as being a "usual university early stage technology", but hopes to spin it into a company early next year. ISIS has set up about 70 such companies since 2000, he says, stressing that "taking things out of the university puts them on a commercial basis from day one". And, he adds, creating such technology spin-offs "is something Britain is good at".

A conductive material that can be easily applied could well make solar power a practical partial solution to the huge electricity demand aboard modern aircraft. Noting the downside of traditional ITO-based panels, Ferguson says: "You can't imagine putting a wing inside a vacuum chamber."

He is enthusiastic about OLED lighting applications, given the zinc material's comparative ease of processing and potential for use on large, flexible surfaces, as it is much less brittle than ITO.

In addition, Ferguson says, the material provides a transparent shield against radio frequency radiation. Thus it could be used aboard aircraft to protect avionics from stray radiation emitted by mobile telephones and other electronic devices - or to block incoming signals.

He also agrees that spacecraft solar panels are a potentially exciting application. The hard panels used today need to be elaborately hinged and folded to fit inside a rocket fairing during launch, but flexible panels could open new design avenues. But, muses Ferguson: "Wouldn't it be great if you could deploy these panels like a roll of carpet?"