Recent advances of triplet–triplet annihilation upconversion in photochemical transformations

Triplet–triplet annihilation upconversion (TTA-UC) can upconvert low-energy photons to high-energy photons under low excitation intensity with incoherent light source, which has shown great potential in solar cells, photocatalysis, 3D printing, smart luminescence materials, and biological applications. In this review, we focus on the advances of TTA-UC in the application of photochemical transformation, especially the progress of TTA-UC for photocatalytic production of solar fuels and high value-added compounds and the emerging photochemical preparation of organics and polymers. And last, we summarize the value of TTA-UC approaches in these contexts and make an outlook on the future challenge and potential strategies.