Diffussion of Singlet Excitons in Anthracene Crystals

Abstract

The temperature dependence of the decay time of singlet excitons in anthracene crystals was measured under no suffering of reabsorption effect. It was clarified that the excitons were populated on the two Davydov states in quasi-thermal equilibrium before emission process. Furthermore, probabilities of energy transfer from the exciton to doped acceptors were measured and the values of the diffusion coefficient D of the exciton was estimated as 10⁻¹∼1 cm²/sec which was much larger than that obtained by many researchs. A similar measurement to that by Simpson was carried out by using a pure perylene film instead of the tetracene doped film in the earlier measurement, giving D as 1.5 cm² sec⁻¹. Furthermore, the drift time due to the diffusion of the exciton through a thin anthracene layer was directly observed, giving D as 1.3 cm² sec⁻¹.