Carbon nanotubes (CNT), core–sheath CNT/reduced graphene oxide nanoribbon (RGONR), CNT/RGO composite, and RGO fibers have been compared as counter electrodes to fabricate novel dye-sensitized solar cells. For the I–/I3–electrolyte, the core– sheath CNT/RGONR fiber shows the best catalytic activity, which in turn produces the highest energy conversion efficiency of 5.64%. In contrast, for the organic T–/T2 electrolyte ...