Perovskite/silicon-heterojunction solar cell is a very promising cell structure for using the solar spectrum efficiently and hence improving the energy conversion efficiency. However, perovskite solar cell based on solution technique requires the planar silicon-heterojunction bottom solar cell, which needs a different fabrication process from the textured substrate. In this paper, we developed the high performance planar silicon-heterojunction solar cell by introducing a novel design for the n-type back field and p-type emitter. The results indicate that a wide bandgap and low refractive index nc-SiOx:H for back field improves the open-circuit voltage, fill factor and short-circuit current density by the increased near-infrared long wavelength response. In addition, a nc-Si:H buffer layer between the a-Si:H passivation layer and p-nc-SiOx:H emitter increases the crystallinity in the emitter and then improves device performance further. Combining the developed nc-SiOx:H back field and pnc-Si(O)x:H emitter, we achieved an efficiency of 18.77% (Certified 19.1%) on a smooth c-Si wafer. Realization of perovskite/silicon monolithic tandem solar cells with an over 1.7 V output voltage shows the potential application for solar to fuel generation and it also proves that the above strategies are very effective for improving the performance of bottom cell in the tandem solar cells.