Nav: Home

Efficiently turning light into electricity

October 11, 2018

Perovskites form a group of crystals that have many promising properties for applications in nano-technology. However, one useful property that so far was unobserved in perovskites is so-called carrier multiplication - an effect that makes materials much more efficient in converting light into electricity. New research performed in collaboration between the University of Amsterdam (UA) and Osaka University (OU) and led by prof. Tom Gregorkiewicz (UA, OU) and prof. Yasufumi Fujiwara (OU), has now shown that certain perovskites in fact do have this desirable property.

Crystals are configurations of atoms, molecules or ions, that are ordered in a structure that repeats itself in all directions. We have all encountered some crystals in everyday life: ordinary salt, diamond and even snowflakes are examples. What is perhaps less well-known is that certain crystals show very interesting properties when their size is not that of our everyday life but that of nanometers - a few billionths of a meter. There, we enter the world of nanocrystals, structures that have shown to be extremely useful in constructing technological applications at tiny scales.

Perovskites - named after 19th century Russian mineralogist Lev Perovski - form a particular family of nanocrystals that all share the same crystal structure. At the nanoscale, these perovskites have many desirable electronic properties, making them useful for constructing for example LEDs, TV-screens, solar cells and lasers. For this reason, in the past years perovskite nanocrystals have been studied extensively by physicists.

Carrier multiplication

A property which so-far had not been shown to exist in perovskites is carrier multiplication. When nanocrystals - in solar cells, for example - convert the energy of light into electricity, this is usually done one particle at a time: a single infalling photon results in a single excited electron (and the corresponding "hole" where the electron used to be) that can carry an electrical current. However, in certain materials, if the infalling light is energetic enough, further electron-hole pairs can be excited as a result; it is this process that is known as carrier multiplication.

When carrier multiplication occurs, the conversion from light into electricity can become much more efficient. For example, in ordinary solar cells there is a theoretical limit (the so-called Shockley-Queisser limit) on the amount of energy that can be converted in this way: at most a little of 30% of the solar power gets turned into electrical power. In materials that display the carrier multiplication effect, however, an efficiency of up to 44% has already been obtained.

PhD

This makes it very interesting to search for the carrier multiplication effect in perovskites as well, and that is precisely what dr. Chris de Weerd and dr. Leyre Gomez from the Optoelectronic Materials group led by prof. Tom Gregorkiewicz, in collaboration with the group of prof. Yasufumi Fujiwara, and with support of their colleagues from the National AIST Institute in Tsukuba and Technical University Delft have now done. Using spectroscopy methods - studying the frequencies of the radiation that comes from a material after very briefly illuminating it with a flash of light - the researchers showed that a perovskite nanocrystals made out of cesium, lead and iodine, do indeed display carrier multiplication. Moreover, they argue that the efficiency of this effect is higher than reported thus far for any other materials; with this finding therefore the extraordinary properties of perovskite receive a new boost!

De Weerd, who successfully defended her PhD thesis based on this and other research last week, says: "Until now, carrier multiplication had not been reported for perovskites. That we have now found it is of great fundamental impact on this upcoming material. For example, this shows that perovskites can be used to construct very efficient photodetectors, and in the future perhaps solar cells."
-end-
Reference

The paper in which the researchers report on their findings was published in Nature Communications. Efficient carrier multiplication in CsPbI3 perovskite nanocrystals, C. de Weerd, L. Gomez, A. Capretti, D. Lebrun, E. Matsubara, J. Lin, M. Ashida, F. Spoor, L. Siebbeles, A. Houtepen, K. Suenaga, Y. Fujiwara and T. Gregorkiewicz, Nature Communications, https://doi.org/10.1038/s41467-018-06721-0 .

About Osaka University

Osaka University was founded in 1931 as one of the seven imperial universities of Japan and now has expanded to one of Japan's leading comprehensive universities. The University has now embarked on open research revolution from a position as Japan's most innovative university and among the most innovative institutions in the world according to Reuters 2015 Top 100 Innovative Universities and the Nature Index Innovation 2017. The university's ability to innovate from the stage of fundamental research through the creation of useful technology with economic impact stems from its broad disciplinary spectrum.

Website: http://resou.osaka-u.ac.jp/en/top

Osaka University

Related Solar Cells Articles:

Next gen solar cells perform better when there's a camera around
A literal ''trick of the light'' can detect imperfections in next-gen solar cells, boosting their efficiency to match that of existing silicon-based versions, researchers have found.
On the trail of organic solar cells' efficiency
Scientists at TU Dresden and Hasselt University in Belgium investigated the physical causes that limit the efficiency of novel solar cells based on organic molecular materials.
Exciting tweaks for organic solar cells
A molecular tweak has improved organic solar cell performance, bringing us closer to cheaper, efficient, and more easily manufactured photovoltaics.
For cheaper solar cells, thinner really is better
Researchers at MIT and at the National Renewable Energy Laboratory (NREL) have outlined a pathway to slashing costs further, this time by slimming down the silicon cells themselves.
Flexible thinking on silicon solar cells
Combining silicon with a highly elastic polymer backing produces solar cells that have record-breaking stretchability and high efficiency.
Perovskite solar cells get an upgrade
Rice University materials scientists find inorganic compounds quench defects in perovskite-based solar cells and expand their tolerance of light, humidity and heat.
Can solar technology kill cancer cells?
Michigan State University scientists have revealed a new way to detect and attack cancer cells using technology traditionally reserved for solar power.
Solar cells with new interfaces
Scientists from NUST MISIS (Russia) and University of Rome Tor Vergata found out that a microscopic quantity of two-dimensional titanium carbide called MXene significantly improves collection of electrical charges in a perovskite solar cell, increasing the final efficiency above 20%.
Welcome indoors, solar cells
Swedish and Chinese scientists have developed organic solar cells optimised to convert ambient indoor light to electricity.
Mapping the energetic landscape of solar cells
A new spectroscopic method now makes it possible to measure and visualize the energetic landscape inside solar cells based on organic materials.
More Solar Cells News and Solar Cells Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Climate Mindset
In the past few months, human beings have come together to fight a global threat. This hour, TED speakers explore how our response can be the catalyst to fight another global crisis: climate change. Guests include political strategist Tom Rivett-Carnac, diplomat Christiana Figueres, climate justice activist Xiye Bastida, and writer, illustrator, and artist Oliver Jeffers.
Now Playing: Science for the People

#562 Superbug to Bedside
By now we're all good and scared about antibiotic resistance, one of the many things coming to get us all. But there's good news, sort of. News antibiotics are coming out! How do they get tested? What does that kind of a trial look like and how does it happen? Host Bethany Brookeshire talks with Matt McCarthy, author of "Superbugs: The Race to Stop an Epidemic", about the ins and outs of testing a new antibiotic in the hospital.
Now Playing: Radiolab

Speedy Beet
There are few musical moments more well-worn than the first four notes of Beethoven's Fifth Symphony. But in this short, we find out that Beethoven might have made a last-ditch effort to keep his music from ever feeling familiar, to keep pushing his listeners to a kind of psychological limit. Big thanks to our Brooklyn Philharmonic musicians: Deborah Buck and Suzy Perelman on violin, Arash Amini on cello, and Ah Ling Neu on viola. And check out The First Four Notes, Matthew Guerrieri's book on Beethoven's Fifth. Support Radiolab today at Radiolab.org/donate.