Triplet harvesting in nanocomposites of lanthanide-doped SnO2 and light-emitting conjugated polymers

Electroluminescence in organic semiconductor polymers is determined by the fraction of singlet (emissive) and triplet (non-emissive) excitons, generated in accordance with spin statistics. In this presentation, we explore the energy transfer between the metal-oxide nanoparticles and conducting polymers. Lanthanide (Ln3+) doped SnO2 nanocomposites (ca. 20nm spherical particles) were incorporated into luminescent conjugated polymers, such as poly(p-phenylene vinylene) (PPV) and a poly(1,4-phenylene) derivative. It was found that sensitization of both polymer and lanthanide was dependent on the system composition and concentration ratios. There was clear evidence to support successful harvesting of non-emissive polymer triplet states into tuneable, Ln3+ photon emission. The triplet state population and sensitization kinetics were modified by the use of inert polymer cages to reduce the triplet quenching. Proposed mechanisms for the energy transfer are described for each system.