Xinjing Huang, a doctoral student in Forrest’s lab, holds a 20% transparency, 30-year solar cell module that she built.

Engineers study long-lasting, window-friendly solar cells

Solar panels don’t last forever. Companies generally offer 20-25 year warranties on their solar technologies, but the National Renewable Energy Laboratory notes that the systems degrade and produce less energy over time, which often prompts early decommissioning. But a solar cell design from University of Michigan engineers boasts an estimated 30-year lifespan while offering high efficiency. Plus, the innovation would be transparent enough to offer an energy-producing replacement for typical windows.

“With these devices used on windows, your building becomes a power plant,” said Stephen Forrest, electrical engineering professor, in a news release

The problem

Silicon is still the primary material used in solar panels to achieve high efficiency, but it isn’t transparent. Researchers working on transparent window-ready solar panels have been investigating carbon-based materials. But efficient, organic, light-converting materials tend to degrade quickly with use. Thus far, proposed modifications to the materials haven’t resulted in much less degradation, the researchers say. 

The technology

The University of Michigan engineers aimed to better understand degradation in organic solar cells and looked at factors including the interactions between materials and the cells’ design.

They studied degradation in “unprotected” solar cells — those without buffer layers to protect against chemical changes during operation. Unprotected cells’ efficiency fell to 40% within 12 weeks. The cells with buffer layers and an extra ultraviolet light filtering layer maintained up to 94% efficiency.

What’s next

A lot of additional research is needed before these 30-year transparent solar cells are ready for the marketplace, but Forrest is confident they will be “coming to a window near you.” 

The research team increased the solar cell transparency to 40%, but they would like to achieve 60% transparency. They’re also working to increase efficiency. And the engineers conducted their degradation experiments under simulated sunlight conditions, so they will likely need a proof-of-concept under real-world conditions.