Photophysics of Pentacene-Doped Picene Thin Films

Here, were report a study on picene nanocrystalline thin films doped with pentacene molecules. The thin films were grown by supersonic molecular beam deposition with a doping concentration that ranges between less than one molecule of pentacene for every 10⁴ picene molecules and up to about one molecule of pentacene for every 10² of picene. The morphology and optoelectronic properties of the films were studied as a function of the concentration of dopants. The optical response of the picene films, characterized by absorption, steady-state, and time-resolved photoluminescence measurements, changes dramatically after doping with pentacene. An efficient energy transfer from the picene host matrix to the pentacene guest molecules was observed, giving rise to intense photoluminescence from pentacene. This efficient mechanism opens the possibility to exploit applications where the excitonic states of the guest component, pentacene, are of major interest such as microwave amplification by stimulated emission of radiation. The observed mechanism could also serve as a prototypical system for the study of photophysics of host-guest systems based on different phenacenes and acenes.