Carrier dynamics of composite and nanolayered films of zinc phthalocyanine and C-60 measured by time-resolved terahertz spectroscopy


Lane P. A. , Melinger J. S. , Esenturk O. , Heilweil E. J.

Conference on Organic Photovoltaics X, California, Amerika Birleşik Devletleri, 3 - 06 Ağustos 2009, cilt.7416 identifier identifier

  • Cilt numarası: 7416
  • Doi Numarası: 10.1117/12.845719
  • Basıldığı Şehir: California
  • Basıldığı Ülke: Amerika Birleşik Devletleri

Özet

We present a study of charge transfer and carrier dynamics in films of zinc phthalocyanine (ZnPc) and buckmisnsterfullerene (C-60) investigated by time-resolved terahertz spectroscopy (TRTS). These films are model structures for charge generation layers in organic photovoltaics and their intrinsic properties are therefore of interest. We compare two classes of films: composite films of ZnPc and C-60 prepared by co-evaporation and layered ZnPc/C-60 films prepared by alternating deposition. We find evidence for a short-lived charge transfer state of C-60 that decays within several picoseconds of excitation. In contrast, both composite and multi-layered films have a long-lived THz absorption that depends on the composition and structure of the fims. The optimum composition for charge transfer within composite films is a 1:1 blend of ZnPc and C-60. Amongst the layered films, there is an increase in charge photogeneration with decreasing layer thickness with a sample having ultrathin (2 nm) exhibiting the strongest THz absorption. A much stronger THz absorption signal was obtained from the layered structure than for the best composite film, even both structures contain similar fractions of ZnPc and C-60.