High-efficiency perovskite photovoltaic material also lases

Under intense development as an alternative to silicon for solar cells, perovskite (named for discoverer Lev Perovski) materials have already achieved 17% photovoltaic efficiency and are closing in on commercial silicon's 20% efficiency. These types of solar cells were pioneered by an Oxford research team led by professor Henry Snaith.

70% optical-to-optical lasing efficiency

Now, researchers from professor Sir Richard Friend's group at the University of Cambridge's Cavendish Laboratory (Cambridge, England), working with Snaith's University of Oxford group (Oxford, England), have shown that CH₃NH₃PbI_3-xCl_x perovskite cells can be made into optically pumped vertical-cavity surface-emitting lasers (VCSELs) that convert visible pump light to near-IR laser light with a 70% efficiency.¹

These results raise expectations for even higher solar-cell efficiencies, say the Oxford-Cambridge team; given that perovskite cells are about to overtake commercial silicon solar cells in terms of efficiency after just two years of development, this is a very real prospect.

"This first demonstration of lasing in these cheap solution-processed semiconductors opens up a range of new applications," says lead author Felix Deschler of the Cavendish Laboratory. "Our findings demonstrate potential uses for this material in telecommunications and for light-emitting devices."

Inexpensive solution processing

Most commercial solar-cell materials need expensive processing to achieve a very low level of impurities before they show good luminescence and performance. In contrast, perovskites work well even when very simply prepared as thin films using cheap scalable solution processing.

The researchers found that upon light absorption in the perovskite, electrons and holes are formed very quickly (within 1 ps), but then take anywhere up to a few microseconds to recombine. This is long enough for chemical defects to have quenched the light emission in most other semiconductors, such as silicon or gallium arsenide. "These long carrier lifetimes together with exceptionally high luminescence are unprecedented in such simply prepared inorganic semiconductors," says Sam Stranks, coauthor from the Oxford University team.

Perovskite-based solar cells are being scaled up for commercial deployment by an Oxford spinoff, Oxford PV Ltd. (http://www.oxfordpv.com/). In addition, the Oxford and Cambridge teams are aiming to construct an electrically driven perovskite laser.

More perovskite info

It should also be noted that this month's online Journal of Physical Chemistry Letters has a special section with 22 articles on many aspects of the use of perovskite materials in solar cells (see http://pubs.acs.org/JACSbeta/jvi/issue27.html). Although you'll need to be a subscriber to read the full papers, you can get lots of info for free by just clicking through to the abstracts.

Source: http://www.cam.ac.uk/research/news/revolutionary-solar-cells-double-as-lasers

REFERENCE:

1. Felix Deschler et al., Journal of Physical Chemistry Letters (2014); doi: 10.1021/jz5005285