Solid-state dye-sensitized solar cells using mesoporous TiO₂ films fabricated with amphiphilic rubbery random copolymer

An amphiphilic copolymer, PLMA-POEM, was synthesized with hydrophobic poly(lauryl methacrylate) (PLMA) and hydrophilic poly(oxyethylene methacrylate) (POEM), which is cheap and rubbery state. The copolymers were characterized by using Fourier transform infra-red spectroscopy (FT-IR), ¹H-nuclear magnetic resonance (¹H-NMR) and gel permeation spectroscopy (GPC). The copolymers were used as sacrificial agent to fabricate anatase mesoporous TiO₂ films and, by varying amounts of TiO₂ particles, polymer molecular weight (MW), concentration of the copolymers, various mesoporous TiO₂ films were fabricated. With a low MW polymer, the TiO₂ formed a worm-like structure with smaller pores, whereas an aggregated honeycomb-like TiO₂ with bimodal pores was obtained for the high MW system, characterized by scanning electron microscopy (SEM), grazing incidence small-angle X-ray scattering (GI-SAXS) and N₂ adsorption-desorption measurement. With 2μm-thick TiO₂ film, efficiency was 4.2% due to better pore filling of the solid electrolyte and improved light scattering properties. By using a layer-by-layer method, the efficiency was further improved to 5.0% at 7μm thickness.