The advantages of using multi‐quantum‐well or superlattice systems as the absorbers in concentrator solar cells are discussed. By adjusting the quantum‐well width, an effective band‐gap variation that covers the high‐efficiency region of the solar spectrum can be obtained. Higher efficiencies should result from the ability to optimize separately current and voltage generating factors. Suitable structures to ensure good carrier separation and collection and to obtain higher open‐circuit voltages are presented using the (AlGa)As/GaAs/(InGa)As system. Efficiencies above existing single‐band‐gap limits should be achievable, with upper limits in excess of 40%.