Low-Power-Photon Up-Conversion in Dual-Dye-Loaded Polymer Nanoparticles

Sensitized triplet–triplet annihilation in multicomponent organic systems is already demonstrated to be suitable for obtaining efficient up-conversion in solution with excitation power densities comparable to solar irradiance, but loses efficiency in the solid state. Here, it is demonstrated that it is possible to reduce this limitation by incorporating a standard bicomponent system in polymer nanoparticles. The confinement of all of the involved photophysical processes in a nanometer-scale volume makes each nanoparticle a single and isolated high-efficiency up-converting unit. As a consequence, these dual-dye-loaded nanoparticles can be used to produce drop-cast films, as well as dopants for polymeric matrices, preserving the performances of the starting moieties in solution.