Ultrafast Energy Transfer Process in Doped-Anthracene Nanoaggregates is Controlled by Exciton Diffusion: Multiple Doping Leads to Efficient White Light Emission

Abstract

Quite similar structures of polycyclic aromatic hydrocarbons make them suitable for doping of one molecule into the crystalline structure or aggregate of another and tuning of the optical properties of the composite system. Anthracene nanoaggregates, singly or multiply doped with perylene, tetracene, and pentacene, have been synthesized using reprecipitation technique. Following photoexcitation of anthracene molecule in the nanoaggregate, anthracene exciton transfers energy to the dopant molecule(s). Energy transfer (ET) efficiency of about 98% could be achieved with the concentration of about 6 × 10–3 mol dm–3 for perylene or tetracene as the acceptor and about 92% efficiency with the doping concentration of about 5 × 10–2 mol dm–3 for pentacene as the acceptor. Very fast energy transfer rates (∼3–6 × 1011 dm3 mol–1 s–1) observed here could not be explained by invoking Forster’s energy transfer mechanism. However, the rate of diffusion of anthracene exciton determined experimentally using exciton–exciton...