A method of depositing a kesterite film which includes a compound of the formula: Cu2-xZn1+ySn(S1-zSez)4+q, wherein 0≦x≦1; 0≦y≦1; 0≦z≦1; −1≦q≦1. The method includes contacting hydrazine, a source of Cu, and a source of at least one of S and Se forming solution A; contacting hydrazine, a source of Sn, a source of at least one of S and Se, and a source of Zn forming dispersion B; mixing solution A and dispersion B under conditions sufficient to form a dispersion which includes Zn-containing solid particles; applying the dispersion onto a substrate to form a thin layer of the dispersion on the substrate; and annealing at a temperature, pressure, and length of time sufficient to form the kesterite film. An annealing composition and a photovoltaic device including the kesterite film formed by the above method are also provided.