perovskite cells
Source: Tor Vergata University of Rome

These flexible perovskite solar cells can power indoor IoT devices

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As connected devices become more commonplace in the home, so too grows energy use and with it, electricity bills and associated emissions.

But what if those devices came with specialised solar cells that could harvest light indoors to help power them?

This is a reality that is now one step closer, as outlined in a recent paper published by a team of German, Italian and Colombian researchers in April.

The flexible cells developed by the researchers, which are made of ultra-thin perovskites, perform better in poor light than the crystalline silicon solar cells typically used on rooftops.

Because perovskites can easily degrade when exposed to UV light, moisture, oxygen and other challenging environments, their use for indoor cells is also a more suitable application.

While crystalline silicon solar cells perform at their best under the bright light of the midday sun, the cells developed by the team led by Thomas Brown, engineering professor at the University of Rome Tor Vergata, were shown to have 20% efficiency at just 200 lux, the typical measure for light inside a home.

As the researchers note, the growth of the IoT industry will result in billions of wireless sensors and devices that require a low-cost and light-weight source of energy.

Currently, indoor IoT devices are often either powered by the electricity grid, or with batteries, some of which may be rechargeable but all of which contain minerals that require more energy to be expended in order to recycle.

Perovskites have an advantage over silicon crystalline cells not only in their ability to harvest energy at low light, but also in their ability to be produced at a relatively low cost.

“In addition to their outstanding performance in indoor environments, PSCs also bring the advantage of solution processability and low cost compared to first- and second-generation PV,” write the researchers.

While the researchers say that high efficiencies have been reported on rigid substrate solar cells indoors, the design of IoT devices would be better made easier by being able to use lightweight flexible cells.

“Thin flexible substrates also enable low-cost fabrication processes, such as roll-to-roll (R2R) manufacturing,” the researchers write.

However, the researchers point out that while many of the materials required for the production of transport and scaffold layers (such as metal oxides) need to be produced under high temperatures, flexible substrates often degrade badly when processed at temperatures higher than 150°C.

While low-temperature fabrication processes on flexible polymeric films (such as PET) or even on unconventional surfaces such as paper, is possible, researchers say the loss in efficiency is unacceptable.

To solve this problem, the researchers say they have developed an alternative to PET, by using ultra-thin flexible glass which can withstand high temperatures up to 700°C.

The use of ultra-thin glass as a substrate follows past research by Brown’s team in Rome that studied the use of flexible glass just 100 micrometres wide for perovskite solar cells in 2018.

Citation: https://doi.org/10.1016/j.xcrp.2020.100045


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Bridie Schmidt

Bridie Schmidt specialises in writing about new technology and how it can help solve the problems of carbon emissions and climate change. With a degree in Communications from Macquarie University, and 20 years experience in front end web development, she has freelanced as a web and graphic designer since 2001. She has been writing about electric vehicles since 2018, has a keen interest in the role that zero emissions transport has to play in sustainability and is co-organiser of the Northern Rivers Electric Vehicle Forum. You can email Bridie at [email protected].

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