An international team including researchers from the University of Toronto’s Faculty of Applied Science & Engineering has developed a perovskite solar cell that can withstand high temperatures for more than 1,500 hours—a significant milestone as this emerging technology approaches commercial application.
The team’s findings were recently published in the journal Science.
“Perovskite solar cells offer new ways to overcome some of the efficiency limitations of silicon-based technology, which is the industry standard today,” said Ted Sargent, a University Professor in the department of electrical and computer engineering at Edward S. Rogers Sr. who recently joined the departments of chemistry and electrical and computer engineering at Northwestern University.
“But given its multi-decade head start, silicon still has an advantage in some areas, including durability. This study shows how we can close that gap.”
Traditional solar cells are made of high-purity silicon wafers that are energy-efficient to manufacture. In addition, they can only absorb certain parts of the solar spectrum.
In contrast, perovskite solar cells are made of layers of nanoscale crystals, making them more amenable to cheap manufacturing methods. By adjusting the size and composition of these crystals, researchers can also tune the wavelength of light they absorb.
It is also possible to place perovskite layers on top of each other, or even on top of silicon solar cells, which enables them to use more of the solar spectrum and further increase their efficiency.
In the past few years, advances from Sargent’s lab and others have brought the efficiency of perovskite solar cells within the same range as what silicon can achieve. However, the sustainability challenge has received little attention.
“We wanted to work at high temperatures and high humidity, because that would give us a better idea of which components might fail first, and how to improve them,” said So Min Park, a postdoctoral fellow in Sargent’s lab and one of the three co-lead authors of the study.
“We combined our expertise in materials discovery, spectroscopy and device manufacturing to design and characterize a new surface coating for the surface of perovskites. Our data show that this coating, made of fluorinated ammonium ligands, improves the stability of the overall cell.”
Perovskite solar cells usually have a passivation layer, which surrounds the light-absorbing perovskite layer and acts as a channel for electrons to move around the circuit.
But depending on its composition, as well as its exposure to heat and humidity, the passivation layer can deform in ways that impede the flow of electrons.
“Many groups are using passivation layers made with a lot of ammonium ions, an organic molecule that contains nitrogen,” said Mingyang Wei, a Ph.D. graduated in the department of electrical and computer engineering who is currently a postdoctoral fellow at École Polytechnique Fédérale de Lausanne and co-lead author of the paper.
“Although they form stable 2D structures at room temperature, these passivation layers can be damaged at high temperatures, due to their mixing with the underlying perovskites. What we did was to replace the typical ammonium ions with 3,4,5-trifluoroanilinium. This new passivation layer does not intercalate into the structure of the perovskite thermal crystals.”
The team then tested the performance of the cells using continuous temperature measurements of 85 Celsius, a relative humidity of 50 percent, maximum tracking power-point and a brightness equivalent to full sunlight. In the paper, they reported a T85—the time it takes for the cell’s performance to drop to 85 percent of its original value—of 1,560 hours.
“A typical value for a perovskite cell like this would be something like 500 hours,” Park said. “There are some teams reporting measurements of more than 1,000 hours, but not at temperatures this high.
Park says the team’s passivation layer can be combined with other innovations, such as double- or triple-junction designs, to further improve perovskite solar-cell performance.
“We still have a long way to go before we can fully replicate the performance of silicon, but progress in this field has been very rapid in the last few years,” he said.
“We are moving in the right direction, and this study will hopefully point the way forward for others.”
More information:
So Min Park et al, Engineering ligand reactivity enables high temperature operation of stable perovskite solar cells, Science (2023). DOI: 10.1126/science.adi4107
Provided by the University of Toronto
Citation: Improved stability helps perovskite solar cells compete with silicon (2023, July 20) retrieved 20 July 2023 from https://phys.org/news/2023-07-stability-perovskite-solar-cells-silicon.html
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