Photodynamics of Charge Separation and Recombination in Solid Alternating Films of Phthalocyanine or Phthalocyanine−Fullerene Dyad and Perylene Dicarboximide

Abstract

Alternate bilayer structures of N,N′-bis(2,5-di-tert-butylphenyl)-3,4,9,10-perylene dicarboximide (PDI), free-base phthalocyanines (Pc), and double-linked free-base phthalocyanine−fullerene dyad (Pc−C60) were prepared by the Langmuir−Schäfer method and studied using a range of optical spectroscopy methods including femtosecond pump−probe and up-conversion. An efficient quenching of the PDI fluorescence by Pc and Pc−C60 dyad was observed in both steady-state and time-resolved fluorescence measurements. The quenching takes place in less than a few picoseconds, and is due to energy transfer from perylene dicarboximide to phthalocyanine chromophore in PDI|Pc and PDI|Pc−C60 films. In the PDI|Pc−C60 bilayer structure the energy transfer is followed by a charge separation in the Pc−C60 layer, yielding a long-lived (a few microseconds) intermolecular charge separated state similar to that reported recently for Pc−C60 Langmuir−Blodgett films (Lehtivuori, H.; et al. J. Phys. Chem. C 2008, 112, 9896−9902).