Ending　group　halogenation　is　an　effective　strategy　for　modulating　the　energy　levels,　bandgaps,　and　intermolecular　interactions　of　nonfullerene　acceptors.　Understanding　the　influence　of　different　halogen　atoms　on　the　acceptor　properties　is　of　great　importance　for　designing　high-performance　nonfullerene　acceptors.　Here,　three　acceptor–donor–acceptor　(A-D-A)　type　nonfullerene　acceptors　(M5,　M6,　and　M7),　which　are　constructed　by　using　a　ladder-type　heteroheptacene　core　without　the　traditional　sp3　carbon-bonded　side　chains　as　the　electron-rich　core,　and　2-(3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile　without　or　with　halogen　atoms　as　the　ending　groups.　The　nonfullerene　acceptors　with　chlorinated　(M6)　and　brominated　(M7)　ending　groups　exhibit　broadened　absorption　spectra,　down-shifted　energy　levels,　and　enhanced　molecular　ordering　compared　to　the　counterpart　without　any　halogenated　ending　groups　(M5).　Among　the　nonfullerene　acceptors,　M6　has　the　strongest　intermolecular　π-π　interaction　with　its　shortest　π-π　interaction　distance　and　the　longest　coherent　length　which　are　beneficial　for　enhancing　the　charge　transport　and　therefore　boosting　the　photovoltaic　performance.　An　excellent　power　conversion　efficiency　of　15.45%　is　achieved　for　the　best-performing　polymer　solar　cell　based　on　M6.　These　results　suggest　that　the　halogenated　ending　groups　are　essential　for　high-performance　heteroheptacene-based　nonfullerene　acceptors　considering　their　simultaneous　enhancements　in　both　the　light-harvesting　and　the　charge　transport.　©　2021　Wiley-VCH　GmbH