The　tandem　organic　solar　cell　could　absorb　the　complementarity　sunlight　spectra　by　the　sub-cells　based　on　the　different　energy　gap　of　the　active-layer　materials.　In　this　work,　a　wide-band　gap　of　the　organic　material　PTB7-Th:　PC71BM　is　used　as　the　front　sub-cells　active　layer,　and　the　narrow-band　gap　of　PTB7-Th:　IEICO-4F　is　used　as　the　rear　sub-cells　active　layer.　The　front　and　rear　sub-cells　present　the　complementary　absorption　spectra　leading　to　the　sufficiently　improvement　of　the　sunlight　absorption.　MoO3/Au/ZnO　multilayer　film　is　the　interconnecting　layer.　ZnO　film　was　prepared　by　the　sputtering　method　is　smaller　root-mean-square　than　that　of　the　film　prepared　by　the　solution　synthesis,　resulting　in　a　good　contact　interfacial　between　the　sub-cells.　This　is　in　favor　of　the　JSC　and　FF　of　the　tandem　organic　solar　cell.　Importantly,　the　short-circuit　current　density　of　the　tandem　solar　cell　is　handily　controlled　by　the　active-layer　concentration　of　the　front　sub-cell,　the　tandem　cell　exhibits　an　optimal　PCE　of　11.77%　with　a　large　VOC　of　1.45 V.　©　2023,　The　Author(s),　under　exclusive　licence　to　Springer-Verlag　GmbH,　DE　part　of　Springer　Nature.