Composites of carbon nanotubes and graphene can give rise to superior function arising from the synergistic effects of the two components. Here, I will present some of our works in investigating the application of carbon nanotube/graphene composites in dye-sensitized solar cells and wearable sensors. The carbon nanotube/grpahene composites prepared by gel coating can effectively catalyze the regeneration of the redox species of dye-sensitized solar cells. They can give rise to a photovoltaic efficiency higher than that with carbon nanotubes, graphene or Pt as the counter electrode. Moreover, we prepare hybrid carbon nanotube/graphene on fibrics. They are sensitive to strain and can be used as washable wearable sensors.