Combining the emerging perovskite solar cell technology with existing silicon approaches in a tandem cell design offers the possibility for new low-cost high-performance devices. In this study, the potential of liquid phase crystallized silicon (LPC-Si) solar cells as a bottom cell in an all-thin-film tandem device is investigated. By optimizing the current output of a four terminal tandem using optical simulations and state-of-the-art electrical properties of the top and bottom cells, we show that an efficiency of 23.3% can be reached, where 7.2% are attributed to the LPC-Si bottom cell. Including the potential of future developments of both sub cells, efficiencies of over 28% are estimated. Electrical and optical measurements of the bottom cell are performed by attaching a perovskite and a cutoff filter to the front side of the interdigitated back contacted LPC-Si cells. The measurements using a cutoff filter show a high impact of the filtered incident light spectrum on the open circuit voltage of the LPC-Si cell. A comparison of the simulated and measured absorptance shows that especially the optical properties of the transparent conductive oxides and recombination losses in the LPC-Si cause high current losses. Combining the measured data of the filtered LPC-Si cells and the semitransparent perovskite cells, yields a realistic estimation for the efficiency of a state-of-the-art four-terminal tandem device of 19.3%.