This disclosure relates to the manufacture an alkali metal quaternary crystalline nanomaterial. an alkali metal quaternary crystalline nanomaterial having general Formula A (I.sub.2-II-IV-VI.sub.4); and wherein I is sodium (Na) or lithium (Li), II and IV are Zn or Sn, and VI is a chalcogens selected from the group comprising: sulphur (S), selenium (Se) or tellurium (Te). The crystal phase of the alkali metal quaternary crystalline nanomaterial may be a primitive mixed CuAu like structure (PMCA) and may have a space group: P42m. The nanomaterials may be adapted to provide a solar cell. Methods of manufacture are also provided.