Sn doped CuGaS₂ has been investigated as an intermediate band (IB) material. Our results indicate that Sn doping can indeed induce IBs in the band gap of CuGaS₂ and the optical absorption and solar energy utilization are greatly enhanced due to the existence of the IBs. Though all Sn doped structures concerned are dynamically stable, we found that under thermal equilibrium growth conditions, the CuGaS₂ should be moderately doped to maintain its stability over a chemical potential region in order to achieve novel optoelectronic IB materials growth.