Layered perovskite-on-silicon could boost photovoltaic efficiencies to 30 percent
http://arstechnica.com/science/2016/01/layered-perovskite-on-silicon-could-boost-pv-efficiencies-to-30-percent/
Layered perovskite-on-silicon could boost PV efficiencies to 30 percent
by John Timmer - Jan 7, 2016 2:52pm EST
Given how fantastically cheap silicon-based photovoltaic cells have gotten, it might be hard to muster much excitement for developing any other material. But the cost of silicon-based PV has created a potential niche—it's so cheap that installation costs now dominate the price of solar power. If we could squeeze more energy out of a single installation, it could drop the costs even further.
That's one of the reasons researchers have been trying to develop perovskites. Not only are these made from chemicals that are cheap and easy to manufacture, there are indications that they can be tuned to absorb some wavelengths while allowing others to pass through to an underlying silicon photovoltaic. The big problem: they tend to decompose when exposed to intense light.
Now, an Oxford-Berlin collaboration is reporting they may have solved the decomposition problem and, in the process, accidentally made a material where they could tune the absorbance across a wide range of wavelengths. With some additional improvements, they suggest a combined silicon-perovskite cell could reach 30 percent efficiencies—up from the neighborhood of 22 for silicon alone.
Perovskites aren't actually a single material; instead, they're a variety of chemicals that all form a similar crystal structure. For photovoltaics, they're often a mix of lead, bromine or iodine, and a small nitrogen-containing organic molecule. None of these is very expensive, and it's relatively easy to form a layer of perovskite materials using bulk techniques. The best of these materials has photovoltaic efficiencies in the teens. That's lower than silicon, but expectations are that it can be brought up even higher...