Perovskite/Cu(InGa)Se2 (PSC/CIGS) tandem configuration is an attractive way to achieve an ultra-high efficient and cost-effective all-thin-film solar cell. However, the imbalanced efficiencies of the constituent sub-cells and the bandgap mismatch generally limited the achieved overall power conversion efficiency (PCE). Herein, by combining Cl bulk incorporation and piperazinium iodide (PDI) surface treatment for the CsFAPb(IBr)3 system, we have successfully reduced the bulk and interface defect densities and greatly enhanced the open-circuit voltage and thus the PCE of the 1.67 eV-bandgap PSCs. The accompanied high activation energy of ion migration has also led to high photostability with suppressed phase segregation. By integrating a highly efficient and highly infrared transparent 1.67 eV PSC top cell with various bandgap CIGS solar cells of comparable efficiency, we have discovered that a 1.04 eV CIGS bottom cell could reach collaborative bandgap matching and realize a four-terminal tandem cell with 28.4% PCE, so far the highest for PSC/CIGS tandems. Moreover, the achieved well-matched Jsc between top and bottom sub-cells and the adopted inverted-PSC configuration have paved the way for producing highly efficient monolithic two-terminal PSC/CIGS tandem devices in the near future.