What if you could turn common metals, like steel or copper, into mini-solar panels by applying a coating? Professors Nikolai Kouklin, computer science, and Konstantin Sobolev, civil & environmental engineering, stumbled onto a way to do just that.
The coating they developed with Yuting Spiegelhoff, a doctoral student in electrical engineering, is easier to use and cheaper than materials used in traditional solar panels.
The discovery came about by accident.
The research team was originally testing hopeite, a zinc-based mineral used for corrosion protection, when they found it had a photovoltaic effect—producing electricity from light, especially when a particular plant dye was used.
“We didn’t know that the zinc-phosphate would have this photovoltaic effect,” Kouklin said.
The researchers found that layers of hopeite reacts quickly to changing light conditions. Unlike traditional solar cells, it doesn’t require semiconductors or an external power source.
That simplicity matters. Traditional solar cells need semiconductors to convert sunlight into an electrical current. Manufacturing those semiconductors is costly, resource-intensive, and requires ultra-pure water.
The team has filed for a patent through the UWM Research Foundation.
The effect of blackberry juice
The coating’s effect is amplified when the coating is combined with anthocyanin, a natural dye found in blackberries. The pigment alters how the mineral interacts with light, boosting voltage output.
“This opens the door to affordable and widely deployable solar cells,” Kouklin said. “Just think – embedded energy generation on metal roofs, infrastructure, or industrial surfaces.”
The Research Foundation helped kickstart this project with early-stage Catalyst Grant funding that allowed the team to demonstrate key properties and build a prototype. See the publication in Applied Physics Letters.