An intermediate reflector layer (IRL) serves as a spectrally selective layer between the top amorphous cell and bottom nanocrystalline cell in a micromorph silicon thin-film solar cell. In this paper, an IRL periodic design is proposed to achieve better conversion efficiency using thin active layers. The optically simulated short circuit current reaches and three-dimensional electrical analysis shows a promising result. The design methodology used in this paper can be easily applied to different types of IRL materials and extended to triple thin-films solar cells. Finally, the results are compared with state-of-the-art design and further enhancement factors are discussed.