eli5: Do solar panels only work with sunlight, or can they be tuned to capture energy from other wavelengths outside the visible spectrum?
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Yes, they can. What you’re thinking of is something called a thermophotovoltaic cell. Some people have mentioned photovoltaic thermal panels, which are a bit different in function and execution, but also use the infrared region of the solar spectrum for useful work.
Photovoltaic thermal panels absorb infrared energy as heat and use the heat to do useful work (e.g. heating water in a closed heating system). Thermophotovoltaics convert infrared energy directly into electricity via a semiconductor devices that operates on similar principles as classic photovoltaic cells.
So why don’t more people know about photovoltaics? There’s a few reasons. First, the materials used in these cells to get the required material properties are much more scarce and fragile than in photovoltaic cells. Second, the amount of energy that can be harvested by these devices is much lower than cells in the visible range. Third, the fabrication methods necessary to make these cells are extremely elaborate, due in part to the materials’ delicacy and the required structure of the devices.
That said, there is also interesting research being done where thermophotovoltaic devices are used to harvest heat from extremely high temperature processes (e.g. metal foundries). The principle of operation between harvest heat from a foundry furnace and harvesting energy from the sun operates on exactly the same principle. It’s just that the sun is much, much, much, extremely much hotter, so it’s much easier to do with the sun.
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