Chalcogenide glass-ceramic having, for example, the following composition GeSe2—Sb2Se3—CuI, this glass-ceramic comprising at least one crystalline phase, characterised in that the crystallisation rate and the dimensions of the crystals in the crystalline phase are such that the crystals are substantially in contact with each other in such a way that this crystalline phase has an electrical conductivity greater than or equal to 10−4 s·cm−1 which increases under lighting due to the creation of charge carriers within the crystalline phase.