Deducing degradation causes in solar panels
Marco Casareto, a materials science and engineering doctoral student in the Ira A. Fulton Schools of Engineering at Arizona State University, conducts lab experiments on perovskite solar technology. Casareto is working with Nick Rolston, a Fulton Schools assistant professor of electrical engineering, and collaborators from the State University of New York at Buffalo to analyze how a part of the solar panel manufacturing process called laser scribing affects the degradation of perovskite solar technology. Photo courtesy Nick Rolston
Solar power is poised for massive growth. According to the U.S. Energy Information Administration, electricity generation capacity from solar resources is expected to increase by 75% from 2023 to 2025.
Solar panels are traditionally made from silicon, the same material used to make microelectronics such as the computer chips that power the modern world. One of silicon panels’ drawbacks is that they require large and expensive manufacturing infrastructure to build, making production costs and potential supply chain issues prohibitive in the face of increasing demand.
Perovskites are a new material class that shows promise to replace silicon. Perovskites are minerals that can be used to build solar panels with high energy-conversion efficiency at a low cost, with minimal production requirements.
“The draw of perovskites is that they’re accessible,” says Nick Rolston, an assistant professor of electrical engineering in the Ira A. Fulton Schools of Engineering at Arizona State University. “They don’t require sourcing through international supply chains.”
However, experimental perovskite panels have run into a problem: They have a very short service life span, often lasting only about a year. To overcome this limitation, Rolston, a faculty member in the School of Electrical, Computer and Energy Engineering, part of the Fulton Schools, and a team of collaborators are conducting research funded by a U.S. Department of Energy grant into whether part of the manufacturing process is to blame for the rapid decay of perovskite solar panels.
Ascribing perovskite failure to laser scribing
To manufacture a perovskite solar panel, a layer of perovskite is deposited onto a glass panel in a manner similar to spray-painting the glass. Additional layers of conductive material and protective coatings are then added to finish a single perovskite cell.
After all layers are in place, small trenches are cut into the material using a process called laser scribing.
A laser carefully destroys small parts of the solar panel to make room for metal bars called bus bars that run through the panel. Bus bars are used to connect smaller perovskite cells together into a complete panel and direct electricity generated from the panel’s sunlight absorption to wires where it can be sent for storage or consumption.
Rolston and colleagues in the field theorize that the production step of laser scribing weakens the sections of material that have been cut, making them a point ripe for failure under harsh outdoor conditions. The hypothesis arose after a pattern of panel layers was observed delaminating, or breaking apart, beginning where laser scribing occurred.
When a solar panel’s layers delaminate, the process breaks the components’ seal and allows air to flow through the gap, reducing electrical conductivity. The increased air between layers also increases the speed at which panels come apart, resulting in a cycle that decreases a panel’s power-generation abilities faster and faster, accelerating the demise of its useful life.
Building solar panels up to break them down
To test the theory that laser scribing weakens a panel enough to cause the layers to break apart, Marco Casareto, a Fulton Schools materials science and engineering doctoral student working in Rolston’s lab, is leading experiments on perovskite solar devices.
Small-scale perovskite devices with and without laser scribes are tested in a chamber with temperatures that will swing quickly between hot and cold extremes, from minus 40 degrees to 85 degrees Celsius. The process is repeated up to 200 times on each device to simulate the effects of years of exposure to the elements.
The experiments are already underway, and the first results from devices that haven’t been laser scribed show a lack of premature degradation.
Once results are complete from the small devices, Casareto will then put them into a computer model. The model will use the results to simulate how larger perovskite panels the size of a commercially available silicon panel would fare.
In addition to Casareto’s experiments, Wanyi Nie, an associate professor of physics at the State University of New York at Buffalo, and her physics doctoral student Jinrui Bai, are assisting with the project. While Casareto and Rolston focus on physical durability, Nie and Bai are addressing how laser scribing affects perovskite optical and electronic properties, which relate to the physics of electricity generation and flow through devices.
“It’s a great pleasure working with Nick and his group,” Nie says. “His expertise in thermal and mechanical property tests has greatly broadened our understanding of perovskite solar modules.”
Redefining solar technology
The researchers plan to use the knowledge gained from the project, which is scheduled for completion by the end of 2025, to inform future perovskite solar panel designs as research in the field continues.
Rolston’s research group has calculated that perovskite solar technology would need to last for 10 years, operating at 80% or more of its original power generation efficiency, to be a viable replacement for silicon. According to data from dozens of panels tested by the National Renewable Energy Laboratory, or NREL, and Sandia National Laboratories, none have maintained efficiency at or above the threshold beyond 0.6 years, or approximately 7.2 months, of use.
With a need for much more development in perovskite solar technology, Casareto plans to make a career out of research in the field after he graduates.
“There are startups and scientists at NREL we have collaborations with,” he says. “I’m hoping to work more with them and to pursue a career either doing research at the national lab or working for one of those companies doing research and development.”
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