Ultrathin solar cells self-repair radiation damage in space

Third-party testing confirms a high level of resilience to the conditions of space in silicon-based solar cells developed by Arizona-based Solestial.

March 28, 2023 Ryan Kennedy

Image: Solestial

Solestial, a solar energy company for space, announced it received confirmation from the French Alternative Energies and Atomic Energy Commission (CEA) that it has independently validated the ability of its solar cells to resist and repair from radiation damage.

The testing confirmed that the silicon cells effectively anneal radiation damage under sunlight at 194 F (90 C). Annealing is the process of slowly cooling to remove internal stresses of a material.

Solestial’s silicon solar cells open circuit voltage dropped by only 4% and maintained 96% of initial value after being exposed to radiation equivalent to 10 years in low Earth orbit and annealing at 194 F under one Sun illumination equivalent. The company said its 20-micron thick cells demonstrate over 20% efficiency.

The company said the tests demonstrate the feasibility of self-curing solar cells with substantially reduced radiation-induced degradation. This is particularly important for space-based solar cells, which are buffeted by high levels of radiation and are required to operate for long lifecycles.

“Annealing of radiation damage in silicon is straightforward at high temperatures, for example, above 200-250°C, but this is not useful for applications in space as these temperatures are rarely, if ever, experienced in situ,” said Romain Cariou, space silicon solar applications expert, CEA. “The differentiation factor here is that Solestial’s cells can cure radiation damage at normal operating temperatures for solar panels in space.”

Cariou said this response to irradiation cannot be found in current commercial cell technologies. Over the course of a 10-year mission, commonly used III-V multijunction solar panels will lose 10% to 15% of their beginning of life efficiency due to radiation damage alone. For conventional terrestrial silicon solar panels, the damage will be even greater at 35% to 40%. Neither III-V nor terrestrial silicon have shown independent laboratory validation of such significant low-temperature annealing, said Solestial.

“We look forward to further testing with the CEA over the coming months to validate internal annealing results at even lower temperatures. We’re excited to show the space industry the myriad benefits of Solestial’s ultrathin silicon solar cells and blankets,” said Stanislau Herasimenka, co-founder and chief executive officer of Solestial.

The company said another advantage of its technology is that it is silicon-based, while many other solar panels made from space are often made from rarer or more expensive materials like gallium arsenide.

The Tempe, Arizona-based company has been developing its technology for over a decade, beginning its life in Arizona State University. It underwent a $10 million seed funding round in October 2022.

The company said it has been focused on testing and validation of its technology, hiring, and converting hundreds of millions of dollars of letters of intent into binding contracts. Its commercial customers range from startups to major defense primes, and builds on a foundation of more than $2.5 million in small business innovation research (SBIR) contracts with NASA, NSF, and other government agencies.

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