Energy

Quantum dot solar cells break efficiency record, silicon in its sights

Solar cells made with quantum dots have achieved a new record efficiency, and been made more stable at the same time
Solar cells made with quantum dots have achieved a new record efficiency, and been made more stable at the same time

One of the most promising, emerging solar cell technologies has received a major efficiency boost. Engineers at UNIST in South Korea have created quantum dot solar cells with a world record efficiency of 18.1%.

Quantum dots are essentially just tiny, circular semiconductor crystals that are incredibly efficient at absorbing and emitting light. The color of light they interact with can be set by changing their size, which makes them useful in display technologies or as sensors.

But where they might end up being most useful is in solar cells. Most commercial solar cells are made with bulk materials as the light-collecting layer, which means the whole surface absorbs the same wavelengths. But with quantum dots you can have multiple sizes that focus on a different part of the spectrum, boosting potential efficiency. As an added bonus, they’re cheap and easy to manufacture, and can even be made into a sprayable solution.

For the new study, researchers at UNIST tweaked the recipe a bit to improve the technology. Quantum dot solar cells made with organic materials have the highest theoretical efficiency, but unfortunately they suffer from defects that make them less stable in sunlight and weather – not ideal for devices designed to be out in the sun all day. To get around that, these solar cells are usually made with inorganic materials instead, but this limits their efficiency, the team says.

The UNIST team made their quantum dots out of an organic perovskite, and developed a new method for anchoring them to a substrate that allowed the dots to be placed closer together. This boosted the efficiency to a record-setting high of 18.1%, up from 16.6% in 2020. This record has been independently recognized by the National Renewable Energy Laboratory (NREL), which keeps an ongoing chart comparing the efficiency of different technologies.

Even better, the new solar cells were far more stable. They maintained their efficiency for 1,200 hours under normal conditions, and 300 hours at an elevated temperature of 80 °C (176 °F). They performed just as well after two years in storage.

Quantum dot solar cells still have a long way to go to catch up to the everyday silicon solar cells, the latter has had a half-century head-start and is rapidly approaching its theoretical maximum efficiency. Meanwhile, quantum dots have only really been in the lab since about 2010, when they had an efficiency of under 4%. Along with the efficiency gains, the inexpensive and simple manufacturing should help scale up the tech and make a wider range of surfaces photovoltaic.

The research was published in the journal Nature Energy.

Source: UNIST

  • Facebook
  • Twitter
  • Flipboard
  • LinkedIn
5 comments
Ric
One detail missing is the theoretical limit to quantum dot efficiency and how it compares to silicon’s.
TechGazer
The lifespan is still way too low to be useful for power generation. Is there a theoretical limit to their lifespan?
rgbatduke
To be clear, record efficiency for quantum dots, not for all solar cell technologies. If one visits the linked NREL chart, there are LOTS of technologies that can produce higher efficiencies, although many of them may be more expensive and use exotic materials, and few of them are being manufactured "at scale" to make them cost effective for more than limited deployment in cases with special needs (high efficiency at light weight in spacecraft, for example). Perovskites have the advantage of being relatively cheap to make, and stabilizing them AND maintaining high efficiency (IIRC the highest efficiency perovskite cells are already up to well above 20%) has been a priority. Quantum dot technology -- if scalable and stable/robust -- may turn this long awaited corner. But I've learned not to hold my breath waiting for a replacement to giant silicon panels at $1/nominal watt or thereabouts. That's where scalable manufacture is at this point in time, with no immediate replacement to my knowledge on the horizon.
Karmudjun
Very nice article Michael. Efficiency is an important fact in solar cell technology, so is duration of optimal use, ability to recycle components, environmental impact of production, risk to workers producing the solar panels at industrial scale, oh, and yes, real world data on power generation lifespan. Oh, and while we can quantify cost/output/hour, we have no numbers in your article to compare. This appears to be QUITE USEFUL for power generation, if the cost is low enough.
paul314
If cells like this get cheap enough, efficiency doesn't matter as much. Just slather them on most available surfaces, so that the default for buildings, roofs and other structures is that they have collectors on them. And if the cost really goes down, durability isn't that much of a deal either -- there are businesses that put up new billboards and signage every few months or weeks, after all.