Perovskite Solar Films Perform Well In Space

• UC Merced developed metal halide perovskite solar films were exposed to harsh conditions of space for 10 months on the ISS
• Examination of these films shows minimal degradation which was also more than 90% reversible
• These films were made using electrospraying method which the team claims can one day be used by astronauts to produce their own films in the space

Metal halide perovskite solar films, made using gravity defying electrospraying method, deployed outside the International Space Station (ISS) by a graduate student of University of California Merced (UC Merced) are said to have survived for 10 months in space, a feat that could lead to one day astronauts producing their own solar panels in space.

The solar films of hybrid organic-inorganic crystals were made by the team using a process called electrospraying that does not require gravity since it uses an electric field to guide the flow of solvents to create 'extremely smooth' solar energy absorbing films.

Installed by the National Aeronautics and Space Administration (NASA) on a cube outside the ISS, the films were developed by US Merced's perovskite lab of Professor Sayantani Ghosh in collaboration with NASA Glenn Research Center (GRC) and the National Renewable Energy Lab (NREL).

These were sent to the ISS as part of NASA's 13^th Materials International Space Station Experiment (MISSE-13), exposed to extreme temperatures of plus-minus nearly 100º, direct radiation and other hazards.

Installed on the ISS, these samples faced the sun and underwent the same cycle of being exposed to 45 minutes daylight and 45 minutes of night just like the space station, undergoing almost 5,000 of these cycles in the 10 months.

Once returned to the earth and several months of quarantine, the films were tested and found to have undergone only minimal degradation, thanks to the absence of oxygen and moisture in space. Examiners also claim the little damage was more than 90% reversible.

"They sustained more damage sitting on the launchpad in Houston than they did on the ISS," Ghosh said. "In space, you would expect the most damage to come from radiation. But this sample had a thin glass panel in front of it and that absorbed most of the high-energy radiation. The glass actually became yellow. The vacuum in space kept the sample safe. There was some strain on the crystal, but you couldn't see it. We only found it when we did some measurements, and after irradiating it, it recovered."

She added, "In fact, in some cases it was better than the samples that had been left on the ground."

While the results are encouraging, NASA and Ghosh plan to further test more samples and have already sent some on successive MISSE missions. The samples sent include fully operational solar cells without glass in front to protect them from direct radiation.

Scientists that worked on the project believe these perovskite solar films can last a minimum of 10 years in space without significant radiation damage.

William Delmas who helped create samples at GRC and is now working at the Sandia National Lab said these encouraging results show that in future astronauts could use electrospraying method 'either on the space station' or 'perhaps on the moon' to make their own solar films.

NASA aims to develop in situ manufacturing capability in the future when lunar habitats are established, explained UC Merced.

According to Delmas, "With 1 liter of perovskite solution, we can make a football-field-sized sheet of solar absorbers in space — so if this works, we can have all the power we want in space, and the ability to make more."

Findings of this research have now been published in the scientific journal Advanced Energy Materials.