CIGSeS (Cu(In,Ga)(Se,S)(2), (CIGSeS)) absorbers were fabricated by sputtering a quaternary ceramic CIGSe targets and annealing in sulfur-containing atmosphere. Sulfurization was applied at various temperatures to study the variation of composition and microstructure. The performances of cells were also investigated. Sulfurization at high temperature (550 degrees C) benefits the diffusion of S atoms into absorbers. Gallium tends to diffuse towards surface, and Indium towards the back as absorbers annealed at 550 degrees C, leading to an enlarged band gap at the surface. With the improvement of anion-deficiency and the band gap gradient introduced by sulfurization, the conversion efficiency of CIGSeS solar cell reaches 13.9%, with the V-OC 566 mV.