Abstract: A thin film quaternary compound semiconductor comprising arsenic (As), selenium (Se), tellurium (Te) and copper (Cu) atoms with adjustable molar concentrations during processing, whose atomic arrangement is predominantly amorphous, glassy or polycrystalline, and dominated by covalent chemical bonds between the said atoms. The amorphous nature of the atomic arrangement gives predominance to short range atomic order, eliminating the constraints of lattice constant mismatch and polarity mismatch with the substrate, which opens the way to wide chemical compositional adjustments and to lower-cost deposition processes such as thermal evaporation or sputtering.