Spray-on material may lower solar cells cost
Imagine a future when solar cells can be sprayed or printed onto the windows of skyscrapers or atop sport utility vehicles — and at prices potentially far cheaper than today’s silicon-based panels.
It’s not as far-fetched it seems. Solar researchers and company executives think there’s a good chance the economics of the $42 billion industry will soon be disrupted by something called perovskites, a range of materials that can be used to harvest light when turned into a crystalline structure.
The hope is that perovskites, which can be mixed into liquid solutions and deposited on a range of surfaces, could play a crucial role in the expansion of solar energy applications with cells as efficient as those currently made with silicon. One British company aims to have a thinfilm perovskite solar cell commercially available by the end of 2018.
“This is the front-runner of low-cost solar cell technologies,” said Hiroshi Segawa, a professor at the University of Tokyo who’s leading a five-year project funded by the Japanese government that groups together universities and companies such as Panasonic Corp. and Fujifilm Corp. to develop perovskite technology.
Not everyone is sold on perovskite as a gamechanger from the industry’s heavy reliance on silicon photovoltaic cells. That said, recent research pointing to the material’s potential continues to grip the solar energy research community.
The World Economic Forum picked the material as one of its top 10 emerging technologies of 2016. Meanwhile, solar panel makers and top universities in Europe, the U.S. and Asia are racing to commercialize the technology, with researchers churning out as many as 1,500 papers a year on the material.
Perovskite’s usefulness was first hinted at back in 2006 when Tsutomu Miyasaka, a professor at Toin University of Yokohama, was approached by a graduate student interested in testing how well the material could convert sunlight to electricity. Though he’d been testing a number of different materials for solar panels, the Japanese academic had never heard of the synthesized crystal, Miyasaka said in an interview.
The idea to use perovskite, which is based on the same structure as a mineral named after Russian mineralogist Lev Perovski, initially went nowhere. Its structure was poorly understood and the industry had already latched on to silicon as the best material to convert sunlight into electricity.
Silicon solar cells have been around since the early days of the space program and now dominate the industry, with global shipments of solar products expected to have totaled $41.9 billion in 2016, according to market researcher IHS Markit. But they have limitations. For one, tremendous amounts of energy are needed to produce the silicon in solar cells.
Things began to change for perovskite with the first publication of research on the material by Miyasaka’s group in the Journal of the American Chemical Society in 2009.
“We had been turned down by magazines like Nature and Science and I suspect that’s because it was low in efficiency and also the material was unheard of,” Miyasaka said. “We talked about perovskite on many occasions but there was no feedback. Ninety-nine percent of people didn’t understand the structure of perovskite and they decided to ignore it.”
Since then, the buzz has grown, thanks to research showing perovskite can convert sunlight more efficiently than initially thought. The big breakthrough came in 2012 when the material’s conversion efficiency — the portion of sunlight that can be converted into electricity — rose above 10 percent for the first time.
Passing that threshold attracted the attention of researchers toiling away on different types of solar cells that were then yielding lower efficiency, according to Martin Green, a professor at the University of New South Wales who also studies perovskite.
The efficiency of perovskite cells has improved further — exceeding 20 percent in the lab — to reach a level that took silicon cells years to achieve. Though conventional solar cells are still more efficient at about 25 percent, they’ve been stuck at that level for about 15 years, according to the World Economic Forum.