Solar cells based on silicon as those installed on our roofs operate with an efficiency of about 20% to convert sunlight into electrical energy; It took over 20 years to achieve this rate of return.
A new type of solar cell based on perovskite material – named after the scientist Lev Perovski, who discovered the mineral calcium titanate in the Ural Mountains in the 19th century – was recently launched by a team of researchers led by Professor Henry Snaith of the University of Oxford.
Perovskite solar cells are a source of great excitement in the research community because they are already positioning themselves to any length just behind the conventional silicon after reaching 17% efficiency after only two years of research. They open the prospect of economic production solar energy on a large scale.
Now the research team of Professor Sir Richard Friend at the Cavendish Laboratory of Cambridge – in collaboration with the Oxford group Snaith – showed that perovskite cells are capable not only of absorbing light, but also ‘in issue. The results published online in the Journal of Physical Chemistry Letters show that these “miracle cells” can also produce lasers at low prices.
By inserting a thin layer perovskite halide lead between two mirrors, the team produced an optical laser which proves that these cells “have a very efficient luminescence” – up to 70% of light absorbed reissued.
The researchers emphasize the fundamental relationship, revealed by Shockley and Queisser in 1961, between the generation of electric charges after light absorption and the process of “recombination” of these charges to be issued new light. Essentially, if a material is good for converting light into electricity, then it will also be to convert electricity into light.
The lasing properties of these materials raise expectations in even higher efficiency solar cells, said the Oxbridge team.
“This first demonstration of lasing in the treatment cheap semiconductors opens the door to new applications,” said lead author Dr. Felix Deschler the Cavendish Laboratory. “Our results demonstrate the potential use of this material in telecommunications and in light emitting devices.”
Most materials for the manufacture of solar cells requires expensive treatment to obtain a very low and thus achieve good performance luminescence impurity level. Surprisingly, these new materials work well, even if they are prepared very simply as the process of thin films.
The researchers found that when the light absorption in perovskite, two charges (electrons and holes) are formed very rapidly – within 1 picosecond – but then they take a few microseconds to recombine. This is long enough for chemical defects that have stopped the light emission in most other semiconductors such as silicon or gallium arsenide. “This longevity associated with an unusually high luminescence are unprecedented in inorganic single reprocessing semiconductor” said Dr. Sam Stranks, co-author of the team from the University of Oxford.
“We were surprised to find such a high luminescence efficiency in easy to reprocess materials. This has implications in improving the efficiency of solar cells,” said Michael Price, co-author, Cambridge.
And Henry Snaith adds: “This is an excellent luminescent behavior test performance of the solar cell – a poorer luminescence (as in amorphous silicon solar cells) reduces both the quantum yield (current collected) and also cell voltage. ”