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New record efficiency for quantum-dot photovoltaics

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May 27, 2014

Solar cells created from ultra-thin layers of quantum dots (Photo: Chia-Hao Chuang, Depart...

Solar cells created from ultra-thin layers of quantum dots (Photo: Chia-Hao Chuang, Department of Materials Science and Engineering, MIT)

Flexible, inexpensive, large-area, lightweight solar cells are difficult to produce as they require an inert atmosphere and high temperatures, and they often degrade in a short time after exposure to air. Researchers at MIT, however, have used a new method to craft solar cells from ultra-thin layers of quantum dots in a process that promises to avoid these problems, and at room temperature. At the same time, they have also set a new record of nine percent for the most efficient quantum-dot solar cells produced to date.

This latest research builds on previous work by the Lester Wolfe Professor of Chemistry, Moungi Bawendi in producing quantum dots as thin, uniform coatings with accurately governed properties. Able to be applied to a range of materials, the tiny particles contained in the film are individually very efficient at turning light into electricity.

According to Vladimir Bulovic, Fariborz Maseeh Professor of Emerging Technology in MIT’s School of Engineering, bringing them together in thin coatings "allow them to do what they do as individuals – to absorb light very well – but also work as a group, to transport charges."

As a result of this arrangement, charges are transported across the film to be collected at the edges where they can then be used in a circuit to create an electric current. Although not yet as efficient as standard types of solar cells, with around nine percent of the light energy received by the cells being converted into electric current, it is the degree of improvement in this area in a short amount of time that is the notable aspect.

"Silicon had six decades to get where it is today, and even silicon hasn’t reached the theoretical limit yet," says Bulovic. "You can’t hope to have an entirely new technology beat an incumbent in just four years of development.”

However, it is the ease at which these quantum dots contained in a film are created which is the most impressive aspect of the work to date. Untold opportunities to apply thin, uniform coatings of electricity-generating quantum dots over surfaces – all without the creation limitations of traditional solar cells in regard to atmosphere, degradation, and temperatures – open up potential for consumer, military, and aerospace product manufacture.

A paper on the research was recently published in the journal Nature Materials.

Source: MIT

About the Author
Colin Jeffrey Colin discovered technology at an early age, pulling apart clocks, radios, and the family TV. Despite his father's remonstrations that he never put anything back together, Colin went on to become an electronics engineer. Later he decided to get a degree in anthropology, and used that to do all manner of interesting things masquerading as work. Even later he took up sculpting, moved to the coast, and never learned to surf.   All articles by Colin Jeffrey
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8 Comments

How much energy went into making them compared to how much energy they will produce over their lifetime?

Slowburn
28th May, 2014 @ 12:47 am PDT

I think that is really cool and very green.

BigGoofyGuy
28th May, 2014 @ 05:49 am PDT

The newest generation of solar cells are promising in the sense, and what was already mentioned in the introduction paragraph, that they only use low temperature processes to create thin optical active layers. Quantum Dot solar cells is one these newer approaches which common strategy is to tackle two big problems in the fabrication of solar cells right now.

1) To avoid high temperature processes and that means a lot of energy is saved in fabrication. 2) To reduce the required film thickness which for thin film technologies like this means more than a factor of 10 to 100 compared to the more bulky crystalline solar cells. This is thanks to the more active light absorbing material. The savings in material translates to savings in cost and energy.

The challenge was to fix the stability of the new solar cells in air. The next big challenge is to create Quantum Dots solar cells based on Silicon, an already abundant and inexpensive material.

Fretting Freddy the Ferret pressing the Fret
28th May, 2014 @ 07:21 am PDT

"By engineering the band alignment of the quantum dot layers through the use of different ligand treatments, a certified efficiency of 8.55% has been reached." 8.55% efficiency = High Efficiency???

Tudor Tihan
28th May, 2014 @ 09:39 am PDT

So, why don't these miracle inventions ever make the market?

WonderingWhen
28th May, 2014 @ 10:26 am PDT

9% ? A lot better than 0.4% reported here back in February 21, 2011

Martin Hone
28th May, 2014 @ 07:21 pm PDT

@Tudor from the Wikipedia entry on Photovoltaic_system:

"In 2012, solar panels available for consumers can have an efficiency of up to about 17%, while commercially available panels can go as far as 27%"

They are half as efficient as consumer panels today but also "flexible, inexpensive, lightweight" etc. It's a tradeoff and they are improving quickly. Wikipedia has an article on solar panel efficiency that gives a useful diagram: http://i.imgur.com/bAQwzjq.jpg

Quantum dot is the red diamond on the bottom right.

Daishi
31st May, 2014 @ 01:42 am PDT

Patience, young grasshoppers. It will come.

Fretting Freddy the Ferret pressing the Fret
31st May, 2014 @ 10:07 am PDT
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