Future and challenges for hybrid upconversion nanosystems

To improve the efficiency of photon upconversion, a hybrid approach of combining organic dyes and inorganic nanoparticles is proving successful, especially in the form of dye-sensitized lanthanide-doped upconversion nanoparticles, nanoparticle-sensitized molecular triplet–triplet annihilation systems and metal–organic-framework nanoparticles. In this Review, we survey the latest advances and examine the key factors affecting upconversion...