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Scientists keep on pushing the efficiency of solar panels higher and higher, and there’s a new record to report: a new solar cell has hit 39.5 percent efficiency under the standard 1-sun global illumination conditions.

That 1-sun marker is simply a standardized way of measuring a fixed amount of sunlight, and almost 40 percent of that radiation can now be converted into electricity. The previous record for this type of solar panel material was 39.2 percent efficiency.

There are more types of solar cells around than you might have realized. The type used here, triple-junction III-V tandem solar cells, are often deployed in satellites and space vehicles, though they have plenty of potential here on solid ground as well.

“The new cell is more efficient and has a simpler design that may be useful for a variety of new applications, such as highly area-constrained applications or low-radiation space applications,” says physicist Myles Steiner, from the National Renewable Energy Laboratory (NREL) in Colorado.

The ‘triple-junction’ part of the equation is important in terms of the efficiency of the solar cell. Each junction concentrates on a particular part of the solar spectrum range, meaning that less light is lost and left unused.

Further efficiency gains were made through the use of so-called ‘quantum well’ technologies. The physics behind them is quite complex, but the general idea is that the materials are carefully chosen and optimized, and made as thin as possible. This affects the bandgap, the minimum amount of energy required to excite electrons and get the current flowing.

In this case, the three junctions are made up of gallium indium phosphide (GaInP), gallium arsenide (GaAs) with some extra quantum well efficiencies added, and gallium indium arsenide (GaInAs).

“A key element is that while GaAs is an excellent material and generally used in III-V multijunction cells, it does not have quite the correct bandgap for a three-junction cell, meaning that the balance of photocurrents between the three cells is not optimal,” says physicist Ryan France from the NREL.

“Here, we have modified the bandgap while maintaining excellent material quality by using quantum wells, which enables this device and potentially other applications.”

Some of the improvements added in this latest cell include an increase in the amount of light absorbed without any corresponding voltage loss. Several other technical tweaks were also made to minimize limitations.

It’s the highest 1-sun efficiency of any solar panel cell ever recorded, though we’ve seen higher from more intense solar radiation. While it takes time for technologies to make their way from the lab into actual products, the potential improvements are exciting.

The cells also recorded an impressive 34.2 percent space efficiency, which is what they should achieve when put to use in orbit. Their weight and resistance to high-energy particles make them particularly suited for this task.

“As these are the highest efficiency 1-sun solar cells as of this writing, these cells also set a new standard for achievable efficiency across all photovoltaic technologies,” write the researchers in their published paper.

The research has been published in Joule.

Article by: David Nield

Via: https://www.sciencealert.com/scientists-just-set-a-new-record-for-solar-cell-efficiency

The cells are also sensitive enough to recycle power from artificial light

A new kind of solar cell, that is so thin it can be stuck on walls and windows, with no discernible loss of light, looks set to give green energy a major boost within a decade after a Government-funded breakthrough in the technology.

A hundred times thinner than a human hair, the cell could be put on clothing to power wearable electronics, such as smartwatches and Fitbits, its developers say.

It could be liberally applied to all sorts of surfaces, from industrial solar farm panels to household roofs; from cars and ships to temperature and other smart sensors.

And it could potentially even be used in space to help power telescopes, satellites, and space ships, they suggest.

A breakthrough in the efficiency of this solar cell – which involves tiny crystals containing silver and bismuth metal – means it is now on the brink of being commercially viable to manufacture.

The developers hope they can double the efficiency within five years, making it comparable with the most efficient solar panels currently available.

And while they concede they may not achieve this goal they are confident that, even with much smaller improvements, the cells will be commercially available within a decade.

“This solar cell could revolutionize solar power,” Seán Kavanagh, of University College London, told i.

“They are so cheap and easy to manufacture that they have huge potential to be integrated everywhere in a ‘winning by numbers’ strategy’. They are so flexible and extremely thin that we wouldn’t even notice them,” he said.

“So while the power generated in a given area mightn’t be as high as a dedicated solar farm in the Sahara, the fact they are everywhere – and invisible – means we could still be capturing large amounts of energy with a vast ‘effective surface area’. To use a fishing analogy – instead of fishing for a few really big fish, as a Saharan solar farm does, it’d be like fishing for millions of small fish with a huge net,” added Mr. Kavanagh, a Ph.D. student splitting his research between UCL and Imperial College London.

Researchers not directly involved in the research welcomed the breakthrough and said they, too, were hopeful it could be commercialized within a decade.

Professor Valeria Nicolosi, of Trinity College Dublin, said: “This is an exciting breakthrough which has the potential to transform solar power in the UK and overseas. It is another example of how fundamental studies can lead to work with huge societal impact.”

Dr. Sam Stranks, Cambridge University, added: ‘This is an important breakthrough. If the efficiency can keep being improved, we may well see such technologies competitive in, for example, lightweight and wearable solar applications.”

Using complex computer modeling, researchers were able to significantly increase the efficiency of these new kinds of solar cells, finding that an even, 50/50 spread of silver and bismuth atoms across the material increased how much light the nanocrystals absorbed, allowing more energy to be generated.

The breakthrough brings the efficiency of the cell to 9 percent compared to 1 to 2 percent a decade ago – meaning that 9 percent of the energy from sunlight that it comes into contact with it is converted into electricity.

Conventional solar panels are 20 percent efficient but they need to be more efficient because they are much more expensive and bulky, Mr. Kavanagh says.

However, he is hopeful – although not certain – that the efficiency of his cell can be increased to around 20 percent in five years or so – although a little more than its current level of 9 percent would be fine to commercialize, he argues.

As well as converting natural sunlight into electricity, this new kind of solar cell can harvest artificial light from lightbulbs and use it to generate power indoors. This is something that conventional solar panels can’t do, which requires natural light.

“You could integrate these solar cells into clothes, or wallpaper, for example where you ‘recycle’ the power from indoor lighting,” said Mr. Kavanagh.

“This is particularly useful for ‘Internet of Things’ devices, like wearable electronics, smart sensors, and others where their ‘smart’ function requires electric power. So rather than having loads of devices that need to be plugged into the grid or have batteries replaced, they can power themselves by constant absorbing light energy from the surroundings,” he said.

Mr. Kavanagh worked on the solar technology with researchers at the Barcelona Institute of Science and Technology, Yonosei University in Seoul, and the ICREA in Spain.

The research was funded by the UK Government, the European Research Council, and the European Union’s Horizon 202 program and is detailed in the journal Nature Photonics.

“As we move towards environmentally-friendly, low carbon sources of energy these findings are an important step towards increasing the efficiency of solar power technology,” said Dr. Kedar Pandya, at EPSRC (Engineering and Physical Sciences Research Council), the government research funding body.

“And by potentially reducing our dependency on the toxic or rare elements currently needed to produce solar cells, these findings could also deliver further environmental and cost benefits,” he said.

Seán Kavanagh is a third-year Ph.D. candidate supervised by Professor David Scanlon, of UCL, and Professor Aron Walsh, of Imperial College London, who were co-authors of the paper in Nature Photonics.

Article by: Tom Bawden

Via: https://inews.co.uk/news/environment/new-solar-cell-windows-clothes-green-energy-1470012