As　the　simplest　oligomeric　acceptors,　dimerized　acceptors　(DAs)　are　easier　to　synthesize,　and　more　importantly,　they　can　retain　good　intermolecular　interaction　and　photovoltaic　properties　of　their　parent　small-molecule　acceptors　(SMAs).　Nevertheless,　currently　most　efficient　DAs　are　derived　from　banana-shaped　acceptors　and　they　might　suffer　from　inferior　device　stability　with　high　diffusion　coefficients.　Herein,　we　design　and　synthesize　two　planar　DAs　(DMT-FH　and　DMT-HF)　by　bridging　two　linear-shaped　M-series　SMAs　with　a　thiophene　unit.　The　effects　of　fluorination　position　on　the　diffusion　coefficients,　power　conversion　efficiencies　(PCEs)　and　stability　of　the　DAs　are　systematically　studied.　Our　results　suggest　that　DMT-HF　with　fluorination　on　the　ending　indanone　groups　shows　enhanced　intermolecular　interactions,　improved　PCE　and　stability　compared　with　the　counterpart　(DMT-FH)　with　fluorination　on　the　central　indanone　groups.　Further　optimization　on　the　DMT-HF-based　devices　yields　an　outstanding　PCE　of　17.17　%,　which　is　the　highest　among　all　linear-shaped　SMA-based　DAs.　Notably,　with　the　low　diffusion　coefficient　(3.36×10−24　cm2　s−1)　of　DMT-HF,　the　resulting　device　retains　over　93　%　of　the　initial　PCE　after　5000　h　of　continuous　heating　at　85　°C,　suggesting　its　excellent　thermal　stability.　The　results　highlight　the　importance　of　intermolecular　interaction　and　fluorination　for　achieving　efficient　and　stable　polymer　solar　cells.　©　2024　Wiley-VCH　GmbH.