In the past, solar researchers have been divided into two camps in their pursuit of cheaper solar power. Some have sought solar cells that can be made very cheaply but that have the downside of being relatively inefficient. Lately, more researchers have focused on developing very high efficiency cells, even if they require more expensive manufacturing techniques.
The new material may make it possible to get the best of both worlds—solar cells that are highly efficient but also cheap to make.
One of the world's top solar researchers, Martin Green of the University of New South Wales, Australia, says the rapid progress has been surprising. Solar cells that use the material "can be made with very simple and potentially very cheap technology, and the efficiency is rising very dramatically," he says.
Perovskites have been known for over a century, but no one thought to try them in solar cells until relatively recently. The particular material the researchers are using is very good at absorbing light. While conventional silicon solar panels use materials that are about 180 micrometers thick, the new solar cells use less than one micrometer of material to capture the same amount of sunlight. The pigment is a semiconductor that is also good at transporting the electric charge created when light hits it.
"The material is dirt cheap," says Michael Grätzel, who is famous within the solar industry for inventing a type of solar cell that bears his name. His group has produced the most efficient perovskite solar cells so far—they convert 15 percent of the energy in sunlight into electricity, far more than other cheap-to-make solar cells. Based on its performance so far, and on its known light-conversion properties, researchers say its efficiency could easily rise as high as 20 to 25 percent, which is as good as the record efficiencies (typically achieved in labs) of the most common types of solar cells today. The efficiencies of mass-produced solar cells may be lower. But it makes sense to compare the lab efficiencies of the perovskite cells with the lab records for other materials. Grätzel says that perovskite in solar cells will likely prove to be a "forgiving" material that retains high efficiencies in mass production, since the manufacturing processes are simple.
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