Improving conversion efficiency of dye-sensitized solar cells by metal plasma ion implantation of ruthenium ions

Dye-sensitized solar cells (DSSC) are based on the concept of photosensitization of wide-band-gap mesoporous oxide semiconductors. At present DSSC have ventured into advanced development and pilot production. Our current research emphasizes on improvements on titanium dioxide (TiO2) photosensitivity under visible light irradiation by using metal plasma ion implantation (MPH). The anatase TiO2 electrode was prepared via a sol-gel process and deposited onto indium-tin oxide glass substrates. Subsequently, the as-deposited TiO2 films were subjected to MPII at 20 key in order to incorporate ruthenium (Ru) atoms onto the TiO2 surface layer. The Ru-implanted TiO2 thin film possessed nanocrystalline Ru clusters of 20 nm in diameter and distributed in near surface layer of TiO2 films. The Ru clusters showed effective in both prohibiting electron-hole recombination and generating additional Ru-O impurity levels for the TiO2 band gap structure. A significant reduction of TiO2 band gap energy from 3.22 to 3.11 eV was achieved, which resulted in the extension of photocatalysis of TiO2 from UV to Vis regime. A small drop of photoelectric performance of 8% was obtained due to the incorporation of Ru atoms in the surface layer of TiO2, a similar side effect as observed in the Fe-implanted TiO2. However, the overall retention of the photocatalysis capability is as high as 92% when switch from UV to Vis irradiation. The improvement of the photosensitivity of TiO2 DSSC by means of metal plasma ion implantation is promising. (C) 2011 Elsevier B.V. All rights reserved.