Research Says Highly Efficient Halide Perovskite Solar Cells Are Unstable
It suggests that appropriate molecular engineering can correct instability
Researchers at the Georgia Institute of Technology said they have discovered that halide perovskite solar cells are far less stable than previously thought and revealed the thermal instability that occurs within the cells’ interface layers.
However, they have also offered a path toward reliable and efficient halide perovskite solar technology. Lead halide perovskite solar cells promise superior conversion of sunlight into electrical power.
The research which was published in Advanced Materials has immediate implications for both academics as well as industry professionals working with perovskites in photovoltaics.
Halide perovskite solar cells possess the two necessary ingredients for any successful solar technology — they are both high-performing and low-cost.
But new solar cell materials are in constant competition to match the stability of silicon-based solar cells, which boast more than 25 years of reliability.
The most common strategy for coaxing high conversion efficiency out of these cells is to treat their surfaces with large positively charged ions known as cations.
However, the researchers identified these cations are too big to fit into the perovskite atomic-scale lattice, and, upon landing on the perovskite crystal, it changes the material’s structure at the interface where they are deposited.
The resulting atomic-scale defects limit the efficacy of current extraction from the solar cell.
The researchers’ concern was that during long periods of solar cell operation, the reconstruction of the interfaces would continue, and therefore they sought to understand and demonstrate how this process happens over time.
“Our work revealed that there is concerning instability introduced by treatment with certain cations,” said Carlo Perini, a research scientist in Correa-Baena’s lab and the first author of the paper.
However, the researchers affirmed the good news that, with proper engineering of the interface layer, enhanced stability of this technology is possible in the future.
The researchers learned that the surfaces of metal halide perovskite films treated with organic cations keep evolving in structure and composition under thermal stress.
They saw that the resulting atomic-scale changes at the interface can cause a meaningful loss in power conversion efficiency in solar cells.
Additionally, it was found that the speed of these changes depends on the type of cations used, suggesting that stable interfaces might be within reach with adequate engineering of the molecules.
“We hope this work will compel researchers to test these interfaces at high temperatures and seek solutions to the problem of instability,” Correa-Baena said.
The team hopes their work should point scientists to an area where they can focus on building more efficient and stable solar technologies.
Recently, researchers at the Helmholtz-Zentrum Berlin said that they had produced perovskite solar cells to achieve efficiencies of well above 24%, which are resistant to drop under rapid temperature fluctuations between -60 and +80 degrees Celsius over one hundred cycles.
Researchers at the École Polytechnique fédérale de Lausanne and Sungkyunkwan University in South Korea identified the cause behind the degradation of perovskite solar cells and developed a technique to improve its stability.