February 23, 2015


Printed solar cells poised for a breakthrough (Viviane Richter, 2/23/15, Cosmos)

In one hour the Sun sends enough energy to the Earth to power civilisation for a year - if only we could capture it. More than 50 years after entering the market, silicon solar cells remain our leading solar technology. Could two cheap contenders finally topple silicon from its rooftop perch? [...]

[A]lthough a silicon solar panel bought today might look like one from 20 or 30 years ago, its performance will be light years ahead. By refining the purity of the material, developing surface treatments to maximise light absorption, and improving the panel's backside electronics, researchers have boosted the efficiency of silicon solar cells handcrafted in the lab from 5% in the early days to 25.6% today. The best commercial mass-produced cells hover around 20%.

At the same time, silicon panels have plummeted in price. Prices were already falling when a wave of giant solar panel factories opened in China, just as the global financial crisis flattened demand. Germany's Fraunhofer Institute calculated that a 10 kilowatt rooftop system now costs less than a tenth of its 1990 price. While the flooded post-GFC market was a boon for consumers, it also dried up R&D funding for silicon cells. But demand is now rising again. Richard Corkish, chief operating officer at the Australian Centre for Advanced Photovoltaics, is optimistic that as R&D starts up again, silicon's efficiency will continue to rise with it: "We've come through a dark time but another boom is coming," he says.

But silicon solar cells are facing other challengers. Solar cells made from perovskites - a mineral that typically consists of a precise mixture of lead, iodine and a simple organic component - have jumped from 3% to 20% efficiency after only five years of research, the steepest increase of any solar cell technology to date. "The rise of metal halide perovskites as light harvesters has stunned the photovoltaic community," wrote Michael Gr├Ątzel, solar researcher at the Ecole Polytechnique in Lausanne, Switzerland, in a recent issue of the journal Nature Materials.

Perovskites' promise is that they might soon match silicon's performance, without its costly high-temperature manufacturing step. Perovskite cells can be made by simply printing a layer of perovskite on to a plastic backing.

All the technology has to do is keep increasing efficiency 500% every 50 years and sooner or later you're making real progress.

Posted by at February 23, 2015 5:48 PM

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