Bulk heterojunction (BHJ) photovoltaic cells (PVCs) have been fabricated with a new active layer architecture by introducing 1-dimensional (1D) multi-walled carbon nanotubes (MWCNTs) and 2-dimensional (2D) reduced graphene oxide (rGO) in Poly[3-hexylthiophene-2,5-diyl] (P3HT): Phenyl-C-61-butyric acid methyl ester (PC60BM) blends. The fabricated solar cells revealed a maximum short-circuit current density (J(sc)) of similar to 11.01 mA/cm(2), open-circuit voltage (V-oc) of similar to 0.63 V and fill factor (FF) of similar to 0.5 yielding an efficiency of similar to 4.13%. The improved efficiency has been attributed to the efficient exciton dissociation at the junctions formed by CNTs and rGOs in addition to PC60BM with P3HT. The faster electron-transport by PC60BM and hole by CNT/rGO network in the blend that inhibits the carrier recombination contribute significantly towards the improved performance of the fabricated PVCs. The effect of MWCNTs:rGOs network on the mesoscopic phase distribution of P3HT and PC60BM have also been investigated.