Methods and devices are provided for forming thin-films from solid group IIIA-based particles. In one embodiment, a method is provided for bandgap grading in a thin-film device using such particles. The method may be comprised of providing a bandgap grading material comprising of an alloy having: a) a IIIA material and b) a group IA-based material, wherein the alloy has a higher melting temperature than a melting temperature of the IIIA material in elemental form. A precursor material may be deposited on a substrate to form a precursor layer. The precursor material comprising group IB, IIIA, and/or VIA based particles. The bandgap grading material of the alloy may be deposited after depositing the precursor material. The alloy in the grading material may react after the precursor layer has begun to sinter and thus maintains a higher concentration of IIIA material in a portion of the compound film that forms above a portion that sinters first.