The　proposal　of　the　ferroelectric　photovoltaic　effect　provides　a　spick-and-span　concept　for　breaking　through　the　bottleneck　of　traditional　heterojunction　energy　conversion　and　the　photoelectric　memory　device.　However,　the　wide　bandgap,　low　carrier　transport　capacity,　and　small　photocurrent　of　ferroelectric　materials　limit　its　ferro-electric　photovoltaic　applications.　Here,　chemical　regulation　of　cobalt　substitution　has　been　used　to　effectively　reduce　bandgap　and　improve　ferroelectric　photovoltaic　properties.　High-quality　Co-substituted　BiFeO(3　)epitaxial　films　were　fabricated　by　magnetron　sputtering.　The　enhanced　tetragonality　can　be　obtained　by　introducing　the　chemical　strain　of　cobalt.　The　ferroelectric　properties　of　present　films　have　been　significantly　improved　with　a　fivefold　increase　in　remnant　polarization,　resulting　from　the　enhanced　lattice　distortion　of　the　oxygen　octahedron.　The　enhanced　hybridization　of　electron　orbitals　and　the　atomic　structure　has　been　revealed　by　synchrotron　radiation　and　the　high-resolution　HAADF-STEM.　Intriguingly,　the　optical　bandgap　has　been　reduced　from　1.97　eV　to1.47　eV,　which　is　close　to　the　ideal　bandgap.　The　switchable　ferroelectric　photovoltaic　can　be　realized　by　changing　the　direction　of　polarization,　and　the　open-circuit　voltage　and　short-circuit　current　have　increased　to　1.7　and　1.8　times,　respectively.　This　work　further　reveals　the　application　potential　of　chemical-strain-modulated　epitaxial　films　in　the　field　of　optoelectronics　and　information　storage.