Excitation energy transfer in composite solid films featuring dioxolane-substituted pentacene derivatives

ORGN 80

Mason A. Wolak, mason.wolak@nrl.navy.mil1, Joseph S. Melinger, melinger@ccs.nrl.navy.mil2, Paul A Lane, plane@ccs.nrl.navy.mil1, Leonidas C Palilis, leonidas@ccs.nrl.navy.mil1, Chad A. Landis3, Jared Delcamp3, John E. Anthony, anthony@uky.edu3, and Zakya H. Kafafi, kafafi@ccf.nrl.navy.mil1. (1) Optical Sciences Division, US Naval Research Laboratory, 4555 Overlook Avenue, S.W, Washington, DC 20375, (2) Electronic Science and Technology Division, Naval Research Laboratory, 4555 Overlook Avenue SW, Washington, DC 20375, (3) Department of Chemistry, University of Kentucky, Chemistry Physics Building, University of Kentucky, Lexington, KY 40506

We describe the photophysical properties of solid films of 6,14-bis(triisopropylsilylethynyl)-1,3,9,11-tetraoxa-dicyclopenta[b,m]pentacene (TP-5) and 2,2,10,10-tetraethyl-6,14-bis-(triisopropylsilylethynyl)-1,3,9,11-tetraoxa-dicyclopenta[b,m]pentacene (EtTP-5) dispersed in either tris(quinolin-8-olato)aluminum III (Alq3) or 4,4-bis[N-1-napthyl-N-phenyl-amino]biphenyl (a-NPD). Upon host excitation, bright red emission (lmax = 645 - 655 nm) from the pentacene guest is observed as a result of fast and efficient Förster energy transfer. High photoluminescence (PL) quantum yields (fPL ~ 60 - 90%) are measured at low concentrations (pentacene ~ 0.25 mol%). Dilute films also show that the molecular singlet excited state lifetimes of TP-5 and EtTP-5 in Alq3 or a-NPD are identical (t ~ 18.5 ns). Strong PL concentration quenching and abrupt shortening of the average PL lifetimes of the Alq3 composite films are observed at higher concentrations (TP-5 ≥ 1.00 mol% and EtTP-5 ≥ 1.50 mol%). None of these features are evident when EtTP-5 is dispersed at comparable concentrations in a-NPD, suggesting even dispersal of the guest monomers in this host.