20 Apr 2022
Solar power in space: guidelines to relevant experiments published in Joule journal.
A collaborative research effort to collectively address this important issue involving scientists from the US National Renewable Energy Laboratory (NREL) has presented guidelines to test the radiation-tolerating properties of perovskites intended for use in space.
“Radiation is not really a concern on Earth, but becomes increasingly intense as we move to higher and higher altitudes,” commented Ahmad Kirmani, a postdoctoral researcher at NREL and lead author of the new paper, Countdown to perovskite space launch: Guidelines to performing relevant radiation-hardness experiments, which appears in the journal Joule.
In space, radiation comes from all directions in the form of protons, electrons, neutrons, alpha particles, and gamma rays. This creates an inhospitable environment for many electronic devices, including solar cells. Therefore, as researchers develop new technologies for space applications, careful thought and rigorous testing is needed to be certain the technology can function for an extended period.
“When you try to mimic the radiation in space with an Earth-based test, it’s very challenging because you have to consider many different particles and the associated particle energy, and they have different influences on various layers within the solar cell,” commented Joseph Luther, co-author of the paper and a senior scientist in the Chemical Materials and Nanoscience team at NREL.
The research is the latest collaboration involving NREL scientists interested in putting perovskites into space. Last year witnessed the testing of perovskites for durability in space. The perovskite cells were affixed to the outside of the International Space Station partly to see how they would handle exposure to radiation.
Solar cells that have been used for orbiting satellites or on the Mars rovers, for example, are made from either silicon or III-V materials from the periodic table of elements.
Other researchers have reported that perovskites can tolerate intense radiation with unprecedented durability, but the new Joule paper offers guidelines on exactly how to test them on Earth for the actual complicated radiation spectrum in various space orbits.
“This is an important piece of work,” said Haegel, center director for Materials Science at NREL. “If we want to accelerate our progress in perovskites for space PV, it is important to bring the community together and define the critical questions and experiments. Perovskites are different, in multiple ways, and we have to rethink long-held ideas about how to effectively evaluate solar cells for the radiation environment in space. This paper makes that contribution.”
The researchers relied on simulations run through SRIM, a Monte Carlo simulation that models the passage of ions through matter. Particle accelerators are used to test radiation tolerance, but the researchers said it is crucially important to select the right particle energy and to know how that test condition relates to the complex radiation spectra the panels would be exposed to in space. Work led by Ian Sellers at the University of Oklahoma pointed to the fact that protons should be the initial focus.
The simulations modeled shooting protons with various energies at a perovskite solar cell and determined how the proton beams would interact. High-energy protons went right through the thin perovskite cells in the simulation. The low-energy protons are adequately absorbed and cause damage to the structure of the perovskite, allowing the researchers to then measure how that radiation damage corresponds to the ability of the solar cell to produce electricity.
The NREL statement adds, “High-energy protons create more heat within the perovskite, which creates an added complication in the understanding of radiation tolerance. This differs from conventional solar cells where high-energy protons and electrons are used to determine the effects of radiation.”
The research findings are the first in what will be a long series of steps toward using perovskites in space. “There are many different ways we can construct perovskite solar cells, so we want to develop one that would be specifically best for space,” said Luther. “This goal will involve many iterations between making a new cell, testing the radiation tolerance and using what we learn to improve the cell design.”
Other research will need to be conducted as well, including how well perovskites handle the extreme temperature swings in space.