Solar cells succeed in space

To test if something will work in space, there’s no better option than to send it into space.

That’s what German researchers did with their new design for perovskite and organic solar cells, and the results were encouraging.

The thin-film cells – known as Organic and Hybrid Solar Cells in Space (OHSCIS) – were unfazed by the extreme conditions, producing power both from direct sunlight and from reflective light from the Earth’s surface, they write in a paper in the journal Joule.

And that, they suggest, sets the foundation for future near-Earth application as well as potential deep space missions.

“The rocket was a big step,” says first author Lennart Reb, from the Technical University of Munich. “Going to the rocket was really like going into a different world.”

The rocket in question was launched from northern Sweden last year, reaching an altitude of 240 kilometres. The solar cells are a hybrid of perovskite and organic solar – both seen as emerging technologies. [Earlier this year, as reported in Cosmos, Australian researchers announced a breakthrough in improving the efficiency of perovskite cells.]

Located in the rocket’s payload, the cells withstood the rumbling forces and heat at lift-off then the strong UV light and ultra-high vacuum in space. And they not only operated efficiently, they showed they can function in low light. The team discovered an energy output fuelled by the weak diffuse light reflected from Earth’s surface.

“This is a good hint and confirms that the technology can go into what is called deep space missions… far away from the Sun, where standard solar cells wouldn’t work in,” says Reb’s colleague and the paper’s senior author, Peter Müller-Buschbaum.

The main aim is to reduce the weight of the equipment a rocket carries. Inorganic silicon solar panels currently used in space missions and satellites are efficient but also heavy and rigid. In comparison, hybrid perovskite and organic solar cells are light and flexible.

“What counts in this business is not the efficiency, but the produced electric power per weight, which is called specific power,” says Müller-Buschbaum. “The new type of solar cells reached values between seven and 14 milliwatts per square centimetre during the rocket flight.”

Transferred onto ultra-thin foils, one kilogram of solar cells would cover more than 200 square metres and produce enough electric power for up to 300 standard 100-watt light bulbs, Reb adds. “This is 10 times more than what the current technology is offering.”

The researchers note, however, that the rocket spent only seven minutes in space, and that longer trials are needed to assess the cells’ long-term stability and potential.