New efficiency record edges flexible solar cells closer to the mainstream

New efficiency record edges fl...
Scientists at Empa have developed a new CIGS flexible solar cell with a record efficiency of 21.38 percent
Scientists at Empa have developed a new CIGS flexible solar cell with a record efficiency of 21.38 percent
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Scientists at Empa have developed a new CIGS flexible solar cell with a record efficiency of 21.38 percent
Scientists at Empa have developed a new CIGS flexible solar cell with a record efficiency of 21.38 percent

Solar cells fashioned into thin and flexible films might not just open up new possibilities in the generation of renewable energy, but could also drive down manufacturing costs. One team of scientists in Switzerland has been working to bring the technology's efficiency up to the levels offered by rigid solar cells, and have taken another step toward this goal by setting a new record of 21.4 percent.

The research was carried out at the Swiss Federal Laboratories for Materials Science and Technology (Empa), where scientists have spent years advancing flexible solar cells known as CIGS, made of copper, indium, gallium and selenium. These are among just a handful of thin-film solar cells under mainstream development with flexible applications mind, and the Empa team has been at the cutting edge of this field for over two decades.

Where the best-performing non-flexible solar cells, made with crystalline silicon, can convert light into electricity with an efficiency of up to 26.7 percent, CIGS flexible solar cells aren't quite there yet. The Empa team set a record efficiency of 12.8 percent way back in 1999, 14.1 percent in 2005, 17.6 percent in 2010, 18.7 percent in 2011, 20.4 percent in 2013 and then 20.8 percent in 2019.

As we can see it has been a long road, but the team has now moved a little closer to its end with yet another breakthrough. To fabricate their cells, the scientists use a technique called low-temperature co-evaporation to grow a semiconducting film on top of a thin polymer layer. By tweaking the composition of the film and the alkali dopants used to equip it with electrical properties, the team was able to boost its photovoltaic performance.

The solar cell's efficiency of 21.38 percent remained stable over several months and was independently verified by scientists at Germany's Fraunhofer Institute for Solar Energy Systems. While the work marks yet another record for the Empa scientists and CIGS cells, we have seen other types of flexible cells hit even higher efficiencies, by combining with other photoactive materials such as perovskite. Last year, we saw one of these so-called tandem cells, which could also be layered onto a flexible film, reach an efficiency of 24.16 percent.

In working towards commercial applications for flexible solar cells, scientists imagine putting them to use on roofs and building facades, mobile electronics, aircraft and ground vehicles. In addition to being lighter and adhering to curved or complex surfaces, these cells also lend themselves to cheaper roll-to-roll manufacturing, which could help drive down the costs of renewable energy overall.

The Empa scientists presented their latest work at the the 38th European Photovoltaic Solar Energy Conference and Exhibition this week.

Source: Empa

Although those last few percentage points are nice, the real question is about getting cells up on sun-facing surfaces cheaply. The flexible cells might not need all of the structure that goes with the rigid ones (the actual cells are only a small fraction of the mass of a conventional solar panel).
Thanks Nick - your inspiring articles point out that the real question is whether or not technologies like flexible solar cells are a mature technology or are just a pipe dream. The pipe dream of the late 90's has become a robust enough to achieve a 20% efficiency milestone. Unless Empa is finished innovating, there is still work to be done on efficiency, cost reduction, and info on it's usable lifespan.
Then maybe someone might want to think about application difficulties.....
So, from 12.8 percent in 1999 to 20.8 per cent improvement in 2019. Wow! a whopping 8-9 percent increase in about 20 years! But at what cost. Rigid non-flexible Silicon solar cells does offset the cost involved in setting up and installation of CIGS (CIGS, made of copper, indium, gallium and selenium) solar cells. Indium, Gallium and Selenium are not exactly super abundant. Compared to these, silicon is present almost everywhere. So instead of spending 20+ years on an experimental technology, we should strive to discover useful qualities and properties of abundantly available materials.
if it is flexible, perhaps it could be used to follow the contour of a car's roof? instead of having the car fit the solar panel, have the solar panel fit the car's roof? perhaps fit different buildings unique shapes? I think it has potential.