The impact of back-contact recombination on Cu(In,Ga)Se 2 (CIGS) cells is discussed based on device simulations in which the typical Ga/III grading is considered. When the diffusion length (L n ) is large relative to the absorber thickness, there is room to improve open circuit voltage (V OC ) by preventing back-contact recombination. Whereas with small L n , the impact of back-contact recombination is negligible. Efficiency gains can be realized by employing contact passivation techniques and/or larger conduction band grading which keep electrons away from the back contact.