An ordinary solar cell does one thing: when the sun shines, current flows. Here, when the sun shines, the current flows differently depending on which side you bring the magnet. A layer of fullerene molecules (resembling soccer balls) acts as a mediator: it generates charge carriers under light and passes electrons with a specific spin direction through itself, as if sorting them by their twist.
It turns out that a magnetic field changes this flow by 5% even at room temperature. That's not much, but it's enough for the device to work as a magnetic inverter: current goes one way without a magnet and the other way with a magnet. Under certain illumination, the difference becomes dramatic — current splits in opposite directions, like water at a fork.
Such devices are needed for spintronics — electronics where signals are carried not only by charge but also by electron spin. If we can learn to mix light and magnetism in a single molecule, we'll get sensors that detect both illumination and magnetic fields at once.
Fullerene C60 consists of 60 carbon atoms arranged in a sphere, like a soccer ball. Its discovery earned the Nobel Prize in Chemistry in 1996.