A team of researchers believes that one small materials swap could make perovskite solar cells more practical by replacing a relatively thick tin oxide buffer with an aluminum oxide film just 3 nanometers thick.
If the approach holds up under further testing, it could help future solar devices deliver more power with less material while better protecting delicate cell components.
Here's what to know
According to pv magazine, the proposed inverted perovskite design uses a thin aluminum oxide (AlOₓ) film at the point where the C₆₀ electron transport layer meets the sputtered indium tin oxide contact. The researchers say the atomic-layer-deposited buffer both protects the perovskite and lowers charge recombination at that interface.
Stephanie Essig, the study's corresponding author, told pv magazine: "The novelty of this research lies in demonstrating that the conventional 10 nm to 20 nm thick SnO₂ buffer layer, typically used to prevent sputter damage, can be replaced by a much thinner, yet more uniform AlOₓ layer."
For the tests, the researchers made semi-transparent inverted perovskite solar cells with AlOₓ films that were 1.5 nm, 3 nm, 5 nm, 8 nm, and 15 nm thick. They compared the results with both buffer-free devices and reference cells that used SnOₓ layers of 3 nm, 10 nm, and 20 nm.
They also evaluated how the fabrication process affected results by comparing deposition temperatures of 167°F (75 C) and 176°F (80 C), while refining the technique with a repeated water-pulse sequence.
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More background
Perovskite solar cells have drawn major interest because they could be cheaper and easier to manufacture than some conventional solar technologies. One of the biggest remaining challenges, however, is durability, especially when sensitive layers are exposed to manufacturing steps that can damage them.
A thinner protective layer that still allows efficient charge extraction could simplify device design while helping the cells maintain strong performance. "It was surprising to find that a 3 nm thick AlOₓ layer allows efficient charge-carrier extraction across the C₆₀/ITO interface," Essig said.
More efficient, stable cells can generate more electricity from the same surface area, making the technology valuable for homes, offices, and urban buildings with limited roof or facade space.
Broader adoption of improved solar technology could also reduce reliance on pollution-producing energy sources, which may help improve air quality and lower health risks associated with dirty energy.
What's being done?
The study examined several aluminum oxide thicknesses, measured how changing the process temperature affected performance, and compared the new buffer against the tin oxide layers commonly used to guard against sputter damage.
According to pv magazine, the top inverted cell began with a glass and indium tin oxide substrate coated with a Me-4PACz hole-selective layer and silicon oxide nanoparticles. The stack also included the perovskite absorber, an approximately 1.4-nm aluminum oxide interlayer, and a 20-nm C₆₀ electron-transport layer, followed by a 25-nm atomic-layer-deposited tin oxide layer and a 130-nm silver electrode. Finally, a 100-nm lithium fluoride coating served as an antireflective layer on the glass.
As researchers improve performance and reduce material thickness, it could open the door to more versatile solar products, especially in applications where lightweight or semi-transparent designs are useful.
The team is focused on refining the process and proving the devices can last. As Essig put it: "We plan to further optimize the transparent conductive oxide (TCO) sputtering process to mitigate sputter damage, alongside extended stability testing of device performance."
Where can I learn more?
These stories look at battery-manufacturing coatings, emerging electric vehicle battery chemistries, and breakthroughs in aluminum recycling.
• At the University of Chicago, researchers achieved a novel battery electrolyte that could aid EVs.
• Scientists found a way to turn recycled aluminum foil into useful nanoparticles.
• At Pacific Northwest National Laboratory, researchers transformed scrap metal into advanced aluminum materials with a new process.
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