In order to further improve the PCE of Perovskite solar cells (PSCs),new possible optimization path needs to be found.Here,quasi-heteroface PSCs (QHF-PSCs) is designed by a doublelayer perovskite film.Such brand new PSCs have good carrier separation capabilities,effectively suppress the nonradiative recombination of the PSCs,and thus greatly improve the open-circuit voltage and PCE.The root cause of the performance improvement is the benefit from the additional built-in electric field,which is confirmed by measuring the external quantum efficiency under applied electric field and Kelvin probe force microscope.Meanwhile,an intermediate band gap perovskite layer can be obtained simply by combining a wide band gap perovskite layer with a narrow band gap perovskite layer.Tunability of the band gap is obtained by varying the film thicknesses of the narrow and wide band gap layers.