Poly(vinyl chloride)-graft-poly(N-vinyl caprolactam) graft copolymer: synthesis and use as template for porous TiO2 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 TiO2 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 TiO2 thin films with the anatase phase. A series of porous TiO2 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 TiO2 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 TiO2 film.