March 30, 2014
New Perovskite Solar Cells Can Also Shoot Laser Beams
Brett Smith for redOrbit.com - Your Universe Online
Made from silicon, conventional solar cells are capable of converting 20 percent of the sun’s radiated energy into electricity.
A new type of cell made from a mineral called perovskite has been refined to the point of 17 percent efficiency after just two years of development, and new research published in the Journal of Physical Chemistry Letters has shown that these cells are also capable of emitting light energy – in the form of a laser.
The team concluded that if a material is good at converting light to electric power, then it will likely be good at changing electricity to light. The lasing qualities in these materials also raise objectives for greater solar cell efficiencies, according to the study team.
"This first demonstration of lasing in these cheap solution-processed semiconductors opens up a range of new applications," study author Felix Deschler, a researcher in the Cavendish Laboratory at Cambridge University said in a recent statement. "Our findings demonstrate potential uses for this material in telecommunications and for light emitting devices."
Perovskite is named for 19th century scientist who discovered it, Lev Perovski. Recently, an Oxford University team led by Henry Snaith was able to develop a solar cell using the mineral.
In the new study, the researchers stacked a thin layer of perovskite between two mirrors and were able to produce an optically-driven laser beam, with as much as 70 percent of absorbed light re-released. For commercial cells to achieve this level of performance, it would require expensive processing to remove almost all impurities. The new materials work well by comparison – even when very simply prepared as thin films using relatively cheap processing.
The study team discovered that, upon light absorption in the perovskite, two charges are produced in about 1 picosecond, but then take longer - up to a few microseconds - to recombine. This is of sufficient length for chemical defects to have stopped the light emission in other semiconductors, like silicon.
"These long carrier lifetimes together with exceptionally high luminescence are unprecedented in such simply prepared inorganic semiconductors," said study author Sam Stranks, a researcher from Oxford University.
"We were surprised to find such high luminescence efficiency in such easily prepared materials. This has great implications for improvements in solar cell efficiency," said co-author Michael Price, a researcher from Cambridge.
"This luminescent behavior is an excellent test for solar cell performance – poorer luminescence (as in amorphous silicon solar cells) reduces both the quantum efficiency (current collected) and also the cell voltage,” Snaith said.
The joint UK team said that this new development sets the stage for greater solar cell efficiency from this type of perovskite semiconductor. The effective luminescence itself may result in other applications with broad commercial prospects. One possibility identified by the team is to build an electrically-driven laser.
Earlier last week, a team of researchers in Singapore announced a similar find using perovskite solar cells. That team said the solar cell material glowed brightly when the laser was shone on it.
“What we have now is a solar cell material that can be made semi-translucent,” said Nripan Matthews from the School of Materials Science and Engineering at Nanyang Technological University. “It can be used as tinted glass to replace current windows, yet it is able to generate electricity from sunlight.”