NOVELTY - An ink composition, comprises: a solvent system; metal chalcogenide nanoparticles; metal ions and metal complex ions that are distributed on the surface of nanoparticles and adapted to disperse nanoparticles in solvent system; and a sodium source dispersed in solvent system and/or included in one of the nanoparticle, metal ions and metal complex ions. The metals of the nanoparticles, metal ions and metal complex ions are selected from group I, group II, group III, group IV elements of periodic table, and sodium and include all metal elements of a chalcogenide semiconductor material.    USE - For forming an ink which is useful for forming a chalcogenide semiconductor film that is used for forming a photovoltaic device (claimed).    ADVANTAGE - The ink comprises well dispersed particles and hence can be used to form a chalcogenide semiconductor film in a solution based process this avoids the use of vacuum equipment and thus reduces manufacturing cost as compared to the convention methods for fabricating semiconductor devices.    DETAILED DESCRIPTION - An ink composition, comprises: a solvent system; metal chalcogenide nanoparticles; at least one of metal ion and metal complex ion distributed on the surface of the metal chalcogenide nanoparticles and adapted to disperse the metal chalcogenide nanoparticles in the solvent system; and a sodium source, which is dispersed in the solvent system and/or included in at least one of the metal chalcogenide nanoparticle, the metal ions and the metal complex ions. The metals of the metal chalcogenide nanoparticles, the metal ions and the metal complex ions are selected from group I, group II, group III, group IV elements of periodic table, and sodium and include all metal elements of a chalcogenide semiconductor material. INDEPENDENT CLAIMS are included for the following:    (1) forming an ink, comprising: forming metal chalcogenide nanoparticles; forming at least one of metal ions and metal complex ions; mixing the nanoparticles, the metal ions/metal complex ions, and solvent system of the ink, where metals of the nanoparticles, metal ions and metal complex ions are selected from group I, group II, group III, or group IV of periodic table; repeating at least two of the above steps if metals of the nanoparticles, metal ions and metal complex ions do not include all metal elements of a chalcogenide semiconductor material; and incorporating sodium into at least one of the nanoparticles, metal ions, metal complex ions and solvent system;    (2) forming (m1) a chalcogenide semiconductor film involving: coating a solution containing the ink composition to form a layer on a substrate; and heating the layer to form the chalcogenide semiconductor film; and    (3) forming a photovoltaic device, involving: forming a bottom electrode layer on a substrate; forming a chalcogenide semiconductor film on the bottom electrode according to the method (m1); forming a semiconductor layer on the chalcogenide semiconductor film; and forming a top electrode layer on the semiconductor layer.