Although　ladder-type　heteroarene　building　blocks　without　sp3-hybridized　bridging　atoms　have　been　widely　used　for　the　synthesis　of　polymer　donors,　they　have　rarely　been　applied　for　constructing　non-fullerene　acceptors　(NFAs)　mainly　due　to　the　lack　of　strategies　to　effectively　modulate　self-aggregation　and　crystallinity　of　the　resulting　acceptors.　Herein,　a　novel　sp3-hybridized-carbon-free　ladder-type　skeleton,　benzo[2,1-b:3,4-b＇]bis(4H-dithieno[3,2-b:2′,3′-d]pyrrole)　featuring　with　two　sets　of　neighboring　side-chains,　is　designed　and　successfully　synthesized　as　a　donor　core　for　developing　NFAs　(cis-MH　and　cis-MF).　The　single-crystal　result　shows　that　the　cis-MF　forms　slip-stacked　J-type　aggregates　and　packs　in　an　anti-parallel　＇face-to-face＇　manner　due　to　the　bulkiness　effect　of　neighboring　side-chains.　This　molecular　stacking　mode　effectively　prevents　the　formation　of　oversized　aggregates　in　the　corresponding　active　layer　as　evidenced　by　atomic　force　microscopy　analyses.　Introduction　of　the　fluorinated　terminals　broadens　the　absorption　range　and　increases　the　crystallinity　of　the　acceptor,　thus　greatly　promoting　its　carrier　transport.　As　a　result,　the　cis-MF-based　device　exhibits　a　6-fold　increase　in　power　conversion　efficiency　compared　to　the　cis-MH-based　device.　Overall,　this　work　provides　a　new　molecular　design　strategy　as　well　as　a　novel　sp3-hybridized-carbon-free　ladder-type　building　block　for　developing　efficient　NFAs　that　can　be　used　to　further　advance　the　PCEs　of　polymer　solar　cells.　©　2021　Elsevier　B.V.