Poly(vinyl chloride)-graft-poly(N-vinyl caprolactam) graft copolymer: Synthesis and use as template for porous TiO ₂ thin films in dye-sensitized solar cells

Poly(N-vinyl caprolactam) (PNVCL) side chains were grafted to a poly(vinyl chloride) (PVC) backbone via atom transfer radical polymerization. The synthesized PVC-g-PNVCL graft copolymer was templated for the preparation of porous TiO ₂ thin films, which involved a sol-gel reaction and calcination process. The interaction of the carbonyl groups in the PVC-g-PNVCL with the titania was revealed by FT-IR spectroscopy. X-ray diffraction and transmission electron microscopy analysis showed the formation of porous TiO ₂ thin films with the anatase phase. A series of porous TiO ₂ thin films with different pore sizes and porosities was prepared by varying the solution compositions and were used as photoelectrodes in dye-sensitized solar cells (DSSC) with a polymer electrolyte. The DSSC performed best when using the TiO ₂ film with higher porosity, lower interfacial resistance, and longer electron life time. The highest energy conversion efficiency, photovoltage (V _oc), photocurrent density (J _sc), and fill factor (FF) were 1. 2%, 0. 68 V, 3. 2 mA/cm ², and 0. 57 at 100 mW/cm ², respectively, for the quasi-solid state DSSC with a 730-nm-thick TiO ₂ film.