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

摘要

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, photo voltage (V_(oc)), photo-current 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.