In　this　paper,　we　report　a　simple　method　to　increase　the　power　conversion　efficiency　(PCE)　of　the　polymer　solar　cells　based　on　poly(3-hexylthiophene)　and　[6,　6]-phenyl-C61-butyric　acid　methyl　ester　derivatives　blended　active　layer.　The　approach　includes　using　a　molybdenum　oxide　(MoO3)　and　Poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(4,4-(N-(4-sec-butylphenyl))diphenylamine)]　(TFB)　composites　as　the　hole　transport　layer　(HTL).　Compared　with　that　of　the　device　with　bare　MoO3　HTL,　the　maximum　39 %　increased　of　PCE　is　obtained　when　MoO3/TFB　composites　as　the　HTL　in　the　devices.　The　device　with　MoO3/TFB　shows　the　best　performance　with　a　PCE　of　3.70 %,　an　open-circuit　voltage　of　0.58 V,　and　a　short-circuit　current　density　of　11.39 mA/cm2.　The　intrinsically　mechanisms　behind　PCE　increased　are　due　to　the　improvement　in　the　interface　layer　morphology　and　the　more　appropriately　energy　level　of　the　cells.　©　2015,　Springer-Verlag　Berlin　Heidelberg.