Among their many uses, quantum dots have shown promise as photovoltaic materials in solar cells. Now, researchers at Los Alamos National Laboratory (LANL) have developed a new type of quantum dot solar cell that isn’t made with the toxic elements found in most, while maintaining efficiency.

Quantum dots are tiny, flat, circular semiconductor crystals. They measure just a few nanometers in diameter, and slight changes in their size dictates their color. They’re also very efficient at absorbing and emitting light, which has seen them turn up in devices like TVs, sensors and, of course, solar cells.

The main problem with quantum dot solar cells is that they’re made with toxic elements like lead and cadmium. So, for the new study the LANL team tried a different recipe, making their dots out of copper, indium and selenium that was then layered with zinc.