This paper describes recent results of the numerical simulation of CuInSe2solar cells. A ZnO/CdS/CIS solar cell, for which an experimental illuminated current‐voltage characteristic and a quantum efficiency measurement were available in the literature, was simulated. Using material parameters available in the literature and adjusting the CIS lifetime as well as the thickness of a hypothetical Cu‐poor CIS layer, excellent agreement with experiment was obtained. It should be noted that this is not necessarily a unique representation of the device. The effects of the Cu‐poor layer thickness on cell performance was then examined. It is shown that thin Cu‐poor layers lead to cells with a relatively highVOC, but a relatively lowJSC. Thick Cu‐poor layers lead to cells with a relatively lowVOC, but a relatively highJSC. It is suggested that control of the Cu‐poor layer thickness can lead to a higher efficiency CIS solar cell.