Enhanced efficiency in ZnPc/C60 organic photovoltaic cells incorporating organic interlayers on anode

We demonstrate a clear dependence of the growth and photovoltaic performance of zinc phthalocyanine (ZnPc) films on the presence of dual organic interlayers of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and tetracene on the transparent indium-tin oxide anode. The PEDOT:PSS layer enables the two-dimensional growth of tetracene, which in turn leads to enhanced molecular packing and exciton diffusion in the ZnPc film. Coupled with exciton blocking provided by tetracene, this results in a more than 100% increase in the external quantum efficiency for ZnPc absorption in bilayer ZnPc/C₆₀ devices. The power conversion efficiency is increased from 2.0% to 3.5% for bilayer devices, and from 3.8% to 5.0% for the more efficient planar-mixed devices.