The efficiency of single-junction crystalline silicon (c-Si) solar cells has approached its practical limit.Application of the tandem device architecture,based on the commercially successful c-Si solar cell technology,may allow for an economically feasible route to further improve the performance of solar modules beyond the limits of c-Si technology.Among the candidates for the wide-bandgap top cell of the tandem device,perovskite based solar cells are very promising due to the advantages of high efficiency,high absorption coefficients,a sharp absorption edge,a tunable bandgap,simple preparation process.Theoretical calculations about the maximum attainable perovskite/c-Si tandem cell performance have been published by several authors.This contribution gives a practical evaluation of attainable pervoskite/c-Si module performances based on currently available commercial c-Si solar cells and published device data of perovskite solar cells.The devices are connected using a 4-terminal (4T) method.The performance is calculated on (mini-) module level with verified optical and electrical simulations.Our investigation shows that despite of the high absorption coefficient of CH3NH3Pbl3 (MAPI),the typical MAPI layer thickness of 300 nm in the perovskite top submodule is insufficient to harvest all high-energy photons,leading to a tandem module efficiency loss of over 1%.Compared to parasitic absorption losses caused by transparent conductive oxide (TCO) of top submodules,the TCO-related resistance loss can have larger detrimental impact on the tandem module performance.With state-of-the-art perovskite PV technologies,the aperture-area efficiency of commercially available metal-wrap-through (MWT) c-Si modules can be improved from 19% to 25%.