Photoexcitation Dynamics in Nanolayered C60-Zinc Phthalocyanine Films
Paul A. Lane, Paul D. Cunningham, Joseph S. Melinger, J. P. Kushto, Okan Esenturk, Edwin J. Heilweil
We elucidate charge transfer and photoexcitation dynamics in C60 and zinc phthalocyanine (ZnPc) by transient and continuous wave spectroscopies. We identify an intermolecular charge transfer state of C¬60 by transient absorption and time-resolved THz and show that carrier cooling occurs over tens of picoseconds. We calculate singlet diffusion rates in C60 by modeling the delayed rise in ground state bleaching of ZnPc absorption following C60 excitation. Recombi¬nation dynamics transform from bimolecular to monomolecular as the layer thickness is reduced, revealing a metastable exciplex at the C60/ZnPc interface with a lifetime of 150 s. Nanolayered films have superior carrier photogeneration and mobility compared to co-deposited blends.