New Solar Cells for Space

Peter Müller-Buschbaum (r.) and Lennart Reb in the laboratories of the Institute of Functional Materials at the Technical University of Munich with the payload module “Organic and Hybrid Solar Cells In Space” (OHSCIS) in their hands. (Source: W. Chen, TUM)

Almost all satellites are powered by solar cells – but solar cells are heavy. While conventional high-perfor­mance cells reach up to three watts of electricity per gram, perovskite and organic hybrid cells could provide up to ten times that amount. A research team from the Technical University of Munich TUM and the German Aero­space Center DLR has now tested this type of cell in space for the first time.Perovskite and organic solar cells are promising options for future gene­rations of solar cells. Over recent years, their efficiency has rapidly caught up with that of conven­tional silicon-based cells. “The best perovskite solar cells currently achieve efficiency levels of 25 percent,” says Peter Müller-Busch­baum, Professor of Functional Materials at the TUM Department of Physics. “These thin solar cells, less than one micro­meter thick, applied to ultra-thin, flexible synthetic sheet, are extremely light­weight. They can therefore produce nearly 30 watts per gram.”

This is only possible thanks to a decisive advantage of the new solar cells: Production of silicon solar cells requires very high tempera­tures and elaborate processes. Perovskite cells and organic semi­conductors, on the other hand, can be manu­factured at room tempera­ture from solution. “These organic solu­tions are very easy to process,” explains Lennart Reb. “Thus the techno­logies open up new fields of application in which conven­tional solar cells were simply too unwieldy or too heavy – and that also applies far beyond the aerospace sector.”

Two different types of organic and perovskite solar cells were tested in space for the first time on a research flight as part of the MAPHEUS 8 program at the European Space and Sounding Rocket Range in Kiruna, Sweden. The rocket reached a height of nearly 240 kilo­meters. “Our MAPHEUS program allows us rapidly to implement experi­ments in a zero-gravity environment, offering exciting research findings,” says Andreas Meyer, Head of the DLR Institute of Materials Physics in Space. “This time it went parti­cularly quick: it took us less than a year to progress from the initial idea to the maiden flight of the solar cells as part of the MAPHEUS 8 program.”

“Electrical measure­ments during the flight and the eva­luation after recovery of the rocket showed that perovskite and organic solar cells can achieve their potential in terms of expected perfor­mance in orbit height,” reports Müller-Buschbaum. “Our measurements are therefore of great scientific value.” The solar cells also generated elec­trical energy under diffuse incidence of light. “Cells turned away from the sunlight, which received only sparse lighting exclu­sively from the earth during the flight, still supplied elec­tricity,” says Reb.

Due to their much thinner thickness, the new solar cells could therefore also be used in much dimmer light, for example on missions to the outer solar system on which the sun is too weak for conven­tional space solar cells. According to DLR material scientist Andreas Meyer, “it would not be the first time that inno­vations are first established as space techno­logies but go on to be used around the world in other sectors. One reason for this is probably the very strict requirements that space places on all technical components.” (Source: TUM)

Reference: L. K. Reb et al.: Perovskite and Organic Solar Cells on a Rocket Flight, Joule, online 12 August 2020; DOI: 10.1016/j.joule.2020.07.004

Link: Institute for Functional Materials, Technical University Munich TUM, Garching, Germany • Institute of Materials Physics in Space, German Aerospace Center (DLR), Cologne, Germany

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