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. C 10H 8/C 10D 8/betamethylnaphthalene- d 10) 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% C 10H 8 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 10 2 or more correlated hoppings (retaining directional memory) and is consistent with linewidth information and with time-resolved studies.