Ternary　two-dimentional　(2D)　materials　exhibit　diverse　physical　properties　depending　on　their　composition,　structure,　and　thickness.　Through　forming　heterostructures　with　other　binary　materials　that　show　similar　structure,　there　can　be　numerous　potential　applications　of　these　ternary　2D　materials.　In　this　work,　we　reported　the　structure　of　few-layer　CrPS4　by　X-ray　diffraction,　transmission　electron　microscope,　and　electron-density　distribution　calculation.　We　also　demonstrated　a　new　application　of　the　CrPS4/MoS2　heterobilayer:　visible-infrared　photodetectors　with　type-II　staggered　band　alignment　at　room　temperature.　The　response　of　the　heterostructure　to　infrared　light　results　from　a　strong　interlayer　coupling　that　reduces　the　energy　interval　in　the　junction　area.　Since　the　intrinsic　bandgap　of　individual　components　determines　wavelengths,　the　decrease　in　energy　interval　allows　better　detection　of　light　that　has　a　longer　wavelength.　We　used　photoluminescence　(PL)　spectroscopy,　Kelvin　probe　force　microscopy　(KPFM)　under　illumination,　and　electrical　transport　measurements　to　verify　the　photoinduced　charge　separation　between　the　CrPS4/MoS2　heterostructures.　At　forward　bias,　the　device　functioned　as　a　highly　sensitive　photodetector,　as　the　wavelength-dependent　photocurrent　measurement　achieved　the　observation　of　optical　excitation　from　532　to　1,450　nm　wavelength.　Moreover,　the　photocurrent　caused　by　interlayer　exciton　reached　around　1.2　nA　at　1,095　nm　wavelength.　Our　demonstration　of　the　strong　interlayer　coupling　in　the　CrPS4/MoS2　heterostructure　may　further　the　understanding　of　the　essential　physics　behind　binary-ternary　transition　metal　chalcogenides　heterostructure　and　pave　a　way　for　their　potential　applications　in　visible-infrared　devices.