Side-chain　fluorination　of　nonfullerene　acceptors　(NFAs)　has　been　rarely　reported　to　enhance　their　photovoltaic　performance,　although　it　may　improve　their　backbone　organization　and　carrier　mobilities.　Here,　we　design　new　partially　fluorinated　side　chains　and　incorporate　them　into　M-series　NFAs,　which　are　featured　with　a　ladder-type　heteroheptacene-cored　skeleton　without　sp3-hybridized　carbons.　Compared　with　the　traditional　M-series　acceptor　with　non-fluorinated　side　chains　(MC7F0),　the　NFA　with　partially　fluorinated　side　chains　(MC7F3)　shows　down-shifted　energy　levels,　reduced　miscibility,　and　more　importantly,　improved　backbone　organization,　thereby　leading　to　the　formation　of　a　3D　network　packing　structure　with　enhanced　carrier　transport.　Consequently,　the　MC7F3-based　device　exhibits　a　power　conversion　efficiency　of　17.61%　and　an　excellent　fill　factor　of　79.48%,　both　of　which　are　among　the　best　values　for　all　A-D-A-type　NFAs　reported　so　far.　The　results　highlight　that　side-chain　fluorination　can　efficiently　enhance　π-conjugated　backbone　organization,　improve　intermolecular　interaction,　increase　electron　mobilities,　and　boost　photovoltaic　performance　of　NFAs.　©　2024　Elsevier　Inc.