We have developed a new class of light-emitting diodes (LEDs) based on atomically precise bimetallic gold-copper nanoclusters that exhibit exceptional photo- and thermal stability and strong solid-state luminescence. The solution-processed devices deliver a record external quantum efficiency of about 12.6% and highly saturated red emission at around 668 nm, outperforming previous non-doped nanocluster LEDs. This breakthrough suggests significant potential for these nanoclusters in next-generation electro-optical technologies. Read more at: Advanced Materials