Phase separation of co-evaporated ZnPc:C60 blend film for highly efficient organic photovoltaics

We demonstrate phase separation of co-evaporated zinc phthalocyanine (ZnPc) and fullerene (C-60) for efficient organic photovoltaic cells. With introducing a poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) film and a crystalline copper iodide film on indium tin oxide, 20-nm-thick ZnPc film adopts a lying-down crystalline geometry with grain sizes of about 50 nm. This surface distributed with strong interaction areas and weak interaction areas enables the selective growth of ZnPc and C-60 molecules during following co-evaporation, which not only results in a phase separation but also improve the crystalline growth of C-60. This blend film greatly enhances the efficiencies in photocurrent generation and carrier transport, resulting in a high power conversion efficiency of 4.56% under 1 sun. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4726118]