Methods and devices are provided for forming multi-nary semiconductor. In one embodiment, a method is provided comprising of depositing a precursor material onto a substrate, wherein the precursor material may include or may be used with an additive to minimize concentration of group IIIA material such as Ga in the back portion of the final semiconductor layer. The additive may be a non-copper Group IB additive in elemental or alloy form. Some embodiments may use both selenium and sulfur, forming a senary or higher semiconductor alloy.