Migration-assisted energy transfer at conjugated polymer/metal interfaces

The dynamics of exciton quenching in a conjugated polymer due to the presence of metal films is analyzed using time-resolved photoluminescence. The quenching is governed by direct radiationless energy transfer to the metal and is further enhanced by diffusion of excitons into the depletion area of the exciton population at the polymer/metal interface. The time-resolved luminescence is described by a numerical exciton diffusion model with the energy transfer incorporated via long-range dipole-dipole interaction at the metallic mirror. This allows us to disentangle the contributions from direct energy transfer to the metal and exciton migration, to the exciton quenching process. For an aluminum electrode strong exciton quenching occurs in a region of typically 15 nm, which can be decomposed in a characteristic energy-transfer range of 7.5 nm and an exciton diffusion length of 6 nm.