Self-assembled　monolayers　(SAMs)　are　pivotal　in　optimizing　the　performance　of　organic　solar　cells　(OSCs)　by　minimizing　interfacial　energy　losses,　thereby　enhancing　overall　device　efficiencies.　Herein,　we　develop　three　π-extended　benzocarbazole-based　SAM　molecules,　3DBCP,　3BCP,　and　4BCP,　as　hole　transport　materials　for　OSCs.　The　absorption　properties,　solubility,　magnitude　and　orientation　of　dipole　moment,　as　well　as　energy　level　alignment　of　these　molecules,　are　meticulously　tuned　via　the　synergistic　effects　of　asymmetric　skeletons　and　odd-even　effects.　Among　them,　the　asymmetric　4BCP,　featuring　an　even-numbered　carbon　alkyl　linker,　exhibits　enhanced　solubility,　a　higher　dipole　moment,　and　more　favorable　energy　level　alignment,　thereby　achieving　superior　surface　coverage　and　uniformity　on　indium　tin　oxide　electrodes.　This　optimized　interface　minimizes　contact　defects　between　the　electrode　and　the　active　layer,　facilitating　improved　hole　extraction　and　collection.　OSCs　employing　4BCP　achieve　a　striking　power　conversion　efficiency　(PCE)　of　19.7%,　coupled　with　excellent　storage　stability.　Importantly,　the　scalability　of　this　approach　is　also　validated:　a　1.10　cm2　large-area　device　and　an　11.09　cm2　minimodule　yield　PCEs　of　17.2%　and　15.7%,　respectively.　These　results　highlight　the　practical　potential　of　4BCP　to　enable　scalable,　high-performance　OSCs　suitable　for　industrial　applications.　©　Science　China　Press　2025.