TOF-GISANS Investigation of Polymer Infiltration in Mesoporous TiO2 Films for Photovoltaic Applications

The structure of porous TiO2 films and TiO2:poly(N-vinylcarbazole) (PVK) composite films is investigated with time-of-flight grazing incidence small-angle neutron scattering (TOF-GISANS). The TiO2 films have been prepared by application of a sol-gel process with a diblock copolymer as structure directing agent, and the conductive polymer PVK is infiltrated in the porous network by spin coating and solution casting. The films show a hierarchical pore structure with mesopores 52 nm in size and additional large macropores with a diameter of about 180 nm. By matching the scattering contrast of the TiO2 with the polymer information about the penetration of the polymer in the pores is determined. Whereas in the PVK film prepared by solution casting the pores are filled to a high degree; in the spin coated film, PVK wets only the TiO2 pore walls and forms a solid overlying layer. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1628-1635,2010