Influence of TiO2 nanotube morphology and TiCl4 treatment on the charge transfer in dye-sensitized solar cells

• Published in: Applied physics. A, Materials science & processing Materials science & processing, 2013-09, Vol.112 (3), p.733-737
• Main Authors: Lee, Sun Hong, Chae, Sang Youn, Hwang, Yun Jeong, Koo, Kee-Kahb, Joo, Oh-Shim
• Format: Article
• Language: English
• Subjects: Applied sciences; Characterization and Evaluation of Materials; Condensed Matter Physics; Cross-disciplinary physics: materials science; rheology; Dyes; Electrodes; Energy; Exact sciences and technology; Machines; Manufacturing; Materials science; Morphology; Nanocrystalline materials; Nanoscale materials and structures: fabrication and characterization; Nanostructure; Nanotechnology; Nanotubes; Natural energy; NTA; Optical and Electronic Materials; Photovoltaic cells; Photovoltaic conversion; Physics; Physics and Astronomy; Processes; Solar cells; Solar cells. Photoelectrochemical cells; Solar energy; Surfaces and Interfaces; Thin Films; Titanium dioxide
• ISSN: 0947-8396; 1432-0630
• DOI: 10.1007/s00339-013-7786-0

Dye-sensitized solar cells (DSSCs) were fabricated using TiO 2 nanoparticles (NPs), TiO 2 nanotube arrays (NTAs), and surface-modified NTAs with a TiCl 4 treatment. The photovoltaic efficiencies of the DSSCs using TiO 2 NP, NTA, and TiCl 4 -treated NTA electrodes are 4.25, 4.74, and 7.47 %, respectively. The highest performance was observed with a TiCl 4 -treated TiO 2 NTA photoanode, although in the case of the latter two electrodes, the amounts of N719 dye adsorbed were similar and 68 % of that of the NP electrode. Electrochemical impedance measurements show that the overall resistance, including the charge–transfer resistance, was smaller with NTA morphologies than with NP morphologies. We suggest that a different electron transfer mechanism along the one-dimensional nanostructure of the TiO 2 NTAs contributes to the smaller charge–transfer resistance, resulting in a higher short circuit current ( J sc ), even at lower dye adsorption. Furthermore, the TiCl 4 -treated NTAs showed even smaller charge–transfer resistance, resulting in the highest J sc value, because the downward shift in the conduction band edge improves the electron injection efficiency from the excited dye into the TiCl 4 -treated TiO 2 electrodes.