Flexible solar technology based on perovskite and ultra-thin silicon substrate can be applied to integrated photovoltaic systems, aerospace, drones, airships, etc. Structural designs with high light absorption are important for photovoltaics because flat ultra-thin silicon is less absorbent. At present, the optical management of ultra-thin Tandem batteries has not been reported much. In this study, the bottom cell is composed of an ultra-thin silicon substrate of 5 microns, and the top cell is composed of a 200 nanometer perovskite layer, which is integrated with silver plasmon nanorings. The light absorption enhancement of the top perovskite layer and the bottom monocrystalline silicon layer is designed by finite element analysis.