Metal-induced photoluminescence quenching of organic molecular crystals

We present a detailed study of the thickness dependence of the photoluminescence of ultrathin organic films on Au(111). For the evaluation of the observed intensities a new differential analysis method is introduced. The obtained quantum yield indicates a complete quenching in the thickness range below 4 monolayers (ML) for the two crystal polymorphs and saturates above 12 ML. Several models of energy transfer were applied to our data. We conclude that only consideration of both exciton diffusion and dissociation at the organic-metal interface in combination with classical energy transfer results in a complete and satisfactory description.