Directing singlet excited energy flow in rubrene-perylene dye (DBP) films

Energy transfer between a sensitizer and a triplet annihilator-emitter system is a key process that dictates the design of a light energy upconversion system. Using a combination of steady-state and time-resolved emission experiments, we have now elucidated excited-state interactions between the rubrene dye and a perylene derivative (DBP), which are commonly employed in upconversion molecular assemblies. Quenching of rubrene emission with a concomitant increase in DBP emission in rubrene-DBP films confirms singlet-energy transfer with a singlet energy transfer efficiency as high as 94%. Under low-intensity (steady-state) excitation, the singlet excited state of rubrene acts as a primary donor in the Förster resonance energy transfer process. The rate constant of energy transfer as determined from emission lifetime measurements of rubrene-DBP films was 1.4 × 109 s–1. The factors that control the singlet energy transfer between excited rubrene and DBP and its role in designing light energy harvesting assemblies are discussed.