 For a two layer cell, one layer should be tuned to 1.64 eV and the other at 0.94 eV, with a theoretical performance of 44%.A three-layer cell should be tuned to 1.83, 1.16 and 0.71 eV, with an efficiency of 48%.A theoretical "infinity-layer" cell would have a theoretical efficiency of 68.2% for diffuse light.