Magnesium chloride is used in a variety of situations, from tofu production to de-icing roads. It’s safe for consumption and disposal in the environment — that’s another advantage over the cadmium version, which requires specialized disposal measures, or ironic corporate dumping scams. You’ll pay a health-fad premium for sodium-free magnesium salt at your local grocery store, but manufacturers can buy Mg-Cl for about $1 a kilogram, while cadmium chloride runs $300 for the same amount. Between reduced costs in materials, production, and recycling, this could be a big step toward bringing the costs of solar power to a mass-market level.
The scientists point out that in their solar cell efficiency tests, the cadmium salt film has to be applied under a fume hood with specialized equipment, while the magnesium salt was applied with a hobby sprayer on a desk in the middle of the lab. It’s so safe because it’s, well, sea salt. Brine from specific areas of the world, like the Dead Sea in Jordan and the Great Salt Lake in the United States, is evaporated away to leave salt behind, just as with regular sodium-based sea salts.
Remember: plants are still much better than us at capturing, storing, and using solar energy, and they don’t use a single space-age polymer to do it. Elegance and efficiency in design is all that’s really needed (along with perhaps a few billion years in which to experiment). Finding solutions like this one will be a necessary pat of switching to a cheap and abundant source of power worldwide.