Evaluating the role of energetic disorder and thermal activation in exciton transport

Temperature dependent measurements of the exciton diffusion length (L_D) are performed for three archetypical small-molecule, organic semiconductors: aluminum tris-(8-hydroxyquinoline) (Alq₃), dicyanovinyl-terthiophene (DCV3T), and boron subphthalocyanine chloride (SubPc). The experimental results are well-reproduced with stochastic simulations for L_D by accounting for the presence of energetic disorder and thermal activation within both the inhomogeneously broadened density of states and the rate of intermolecular Förster energy transfer, respectively. In turn, activated and non-activated transport regimes can be distinguished, and exciton energy transfer within these materials can be deconvoluted from energetic disorder - providing insight regarding the fundamental parameters limiting L_D.