Scientists at Tokyo Institute of Technology (Tokyo Tech) have discovered a new alkali copper halide, Cs5Cu3Cl6I2, that emits pure blue light. The combination of the two halide ions, chloride and iodide, gives the material a crystalline structure made of zigzag chains and peculiar properties that result in highly efficient photoluminescence. This novel compound could be readily used to produce relatively inexpensive and eco-friendly white LEDs and reduce the energy used in the generation of everyday artificial light.