The most explored approaches to high-efficiency solar cells have been the stacking of multiple p-n junctions and the concept of intermediate-band solar cell (IBSC). However, both approaches suffer from various material and epitaxial limitations which restrict the power conversion efficiencies from reaching the Shockley-Queisser limit. On the other hand, the series-parallel solar cell tandems have been proposed to effectively use the solar spectrum, while reducing the issues of lattice mismatch and current mismatch. However, the structure optimization has yet been conducted, taking into account the restrictions of current match and voltage match in operation. In this work, we optimize the band-gaps with different spectrums and concentrators by the detailed principles to observe the characteristics of this cell. Compared to the conventional triple junction tandem cells, the series-parallel solar cells significantly improve the current-matching restrictions.