NOVELTY - Precursor material for forming a film of group IB-IIIA-chalcogenide compound, comprises either: (A1) (a) group IB-chalcogenide nanoparticles (104) with an element of group IB, and/or (b) group IIIA-chalcogenide nanoparticles with at least one element of group IIIA, and (c) source of extra chalcogen mixed with group IB chalcogenide nanoparticles and group IIIA-chalcogenide nanoparticles; or (B1) core-shell nanoparticles having core nanoparticles containing at least one element from group IB and/or IIIA and coating of non-oxygen chalcogen and/or chalcogenide material.    USE - The precursor materials are useful for forming a film of a group IB-IIIA-chalcogenide compound (claimed) on a solar cell.    ADVANTAGE - The precursor materials: rapidly fabricate high-quality and uniform copper indium gallium (di)selenide films for solar modules at low temperature; are highly tunable, reproducible and is produced at low cost; and exhibit properties including high density, high uniformity, low porosity and minimal phase segregation.    DETAILED DESCRIPTION - Precursor material for forming a film of a group IB-IIIA-chalcogenide compound, comprises either: (A1) (a) group IB-chalcogenide nanoparticles (104) containing a non oxide chalcogenide material in the form of an alloy of a chalcogen with an element of group IB, and/or (b) group IIIA-chalcogenide nanoparticles containing a non oxide chalcogenide material in the form of an alloy of a chalcogen with at least one element of group IIIA, and (c) a source of extra chalcogen mixed with the group IB chalcogenide nanoparticles and the group IIIA-chalcogenide nanoparticles; or (B1) core-shell nanoparticles having core nanoparticles containing at least one element from group IB and/or IIIA and a coating of a non-oxygen chalcogen and/or chalcogenide material on the core nanoparticles, where the coating provides an extra source of chalcogen.    DESCRIPTION OF DRAWING(S) - The figure shows schematic diagram of the formation of chalcogenide film from binary nanoparticles and chalcogen particles.    Substrate (101)    Binary alloy (102)    Chalcogenide nanoparticles (104)