Solar panels are a great way to capture energy from the sun but they’re far from perfect. A common misconception is that they use the sun’s heat to generate renewable energy when in fact, it’s the light that solar cells are after. Ironically enough, heat is the enemy of solar cells as they become less efficient as they warm up.

In a bid to improve their efficiency, a team of engineers from Stanford have developed a transparent overlay that helps cool the cells as the sun beats down on them.

The overlay is based on a somewhat simple but not always obvious concept. When you step outside, your head emits heat into space as infrared light (think of the sky as a giant heatsink).

The overlay, a thin, patterned silica material, allows the visible sunlight to pass through to the solar cells while simultaneously collecting and emitting heat back into the atmosphere.

The engineers tested the overlay using a custom-made solar absorber which mimics the properties of a solar cell without actually producing electricity. Testing revealed the overlay allowed light to pass through normally but reduced the temperature of the absorber by as much as 23 F.

For a typical solar cell, that level of temperature reduction could improve absolute efficiency by more than one percent. That doesn’t sound like much although if scaled (and if the overlay can be produced affordably), it could deliver a significant gain in energy production.