  Here were report a study of picene nano-cristalline 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
molecules of pentacene every 104 picene molecules up to about one molecule of
pentacene every 102 of picene. Morphology and opto-electronic 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 the
doping with pentacene. An efficient energy transfer from the picene host matrix
to the pentacene guest molecules was observed giving rise to an intense
photoluminescence coming out 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 MASER. The observed
mechanism could also serve as prototypical system for the study of the
photophysics of host guest systems based on different phenacenes and acenes.
