Dynamics of energy transport in ternary molecular solids. I. Naphthalene steady state fluorescence

Abstract

Energy transport experiments were conducted at liquid helium temperatures on ternary single crystals (host/guest/ supertrap, i.e. C10H8/C10D8/betamethylnaphthalene-d10) at guest concentrations of 50--99% and very low (about 10-5) supertrap concentrations. The relative supertrap to guest steady-state fluorescence gives a measure of the exciton percolation probability (migration to the supertrap). The onset of efficient transport is observed at about 85% C10H8 compared to about 50% at higher supertrap concentrations bearing our the kinetic nature of the transport (e.g. dynamic percolation). The wealth of data are well fitted by an effectively two-dimensional percolation formalism containing a single parameter of "coherency", i.e. an exciton mean free path (in nearest neighbor lattice units), extrapolated to the pure crystal (naphthalene). Our result gives about 102 or more correlated hoppings (retaining directional memory) and is consistent with linewidth information and with time-resolved studies.