AbstractWe present a simple yet powerful analysis of Suns‐photoluminescence quantum yield measurements that can be used to determine the surface saturation current densities of thin film semiconductors. We apply the method to state‐of‐the‐art polycrystalline perovskite thin films of varying absorber thickness. We show that the non‐radiative bimolecular recombination in these samples originates from the surfaces. To the best of our knowledge, this is the first study to demonstrate and quantify non‐linear (bimolecular) surface recombination in perovskite thin films.