More than 99% of all renewable energy resources near the Earth’s surface are available in the form of solar radiation. A one percent efficiency increase of direct conversion of solar energy will therefore enhance the theoretical available renewable energy by as much as the potential of all other renewables, including wind, bio, hydro, ocean and geothermal energy, taken together. Our aim is to harvest the untapped parts of the solar spectrum and to transform it into useful photons or charge carriers. Down-conversion through singlet fission and up-conversion through triplet-triplet annihilation are two photophysical processes that have potential to dramatically increase the theoretical limits for any solar energy process. In this presentation, I will show some of our attempts towards diffusion-free triplet-triplet annihilation up-conversion (TTA-UC). By using a supramolecular approach where the sensitizers are non-covalently bound to a dendrimeric annihilator we have addressed the challenge with a systematic approach in which all molecular processes could be studied and optimized separately.