Geminate Triplet Exciton Dynamics in Rubrene Single Crystals

Abstract We present a series of investigations on the intermediate timescale dynamics of geminate triplet exciton pairs in rubrene single crystals. In particular, we report the observation of quantum beats — GHz-timescale oscillations produced by energy splittings — in the photoluminescence of rubrene crystals [7], indicating coherence between triplet pairs which lasts at least 40 ns at room temperature. Additionally, we present long-timescale (up to 10 ? s) measurements of the PL dynamics of rubrene without a contribution from nongeminate triplet fusion; these measurements provide support for a random walk model of triplet diffusion and demonstrate a transition in this diffusion's dimensionality on a timescale of ? ? 2?s.