| AVS 56th International Symposium & Exhibition | |
| Electronic Materials and Processing | Tuesday Sessions |
| Session EM-TuP |
| Session: | Electronic Materials and Processing Poster Session |
| Presenter: | Y. Shigesato, Aoyama Gakuin University, Japan |
| Authors: | Y. Sato, Aoyama Gakuin University, Japan T. Hashimoto, Aoyama Gakuin University, Japan A. Miyamura, Aoyama Gakuin University, Japan Y. Shigesato, Aoyama Gakuin University, Japan |
| Correspondent: | Click to Email |
Dye-sensitized solar cells have attracted attentions as next generation solar cells which have possibility to perform high efficiency with low cost. In recent years, various applications of the cells, such as colorful or flexible solar cells fabricated on polymer substrates, have been suggested. In conventional processes to form the TiO2 photoelectrodes in the cell, the substrates should be annealed at higher temperature than 500 oC, which make it difficult to deposit TiO2 films on polymer substrates. Sputter depositions should have advantages in fabricating the window-size uniform coatings of anatase TiO2 at low temperature. In this study, dye-sensitized solar cells with TiO2 photoelectrodes deposited by reactive magnetron sputtering on flexible substrates were fabricated and characteristics of the cells were investigated. A dual magnetron sputtering (DMS) system was used for the sputter deposition of TiO2 [1-3]. This system consists of two magnetron cathodes with Ti metal targets, a dc power source with a 50 kHz pulse unit and plasma control unit (PCU) with a feedback system of plasma emission intensity (Fraunhofer Institut fur Elektronenstrahl-und Plasmatechnik, FEP). In the PCU, the plasma emission intensity of the Ti line at 500 nm was transformed into photovoltage (OEI) in order to control O2 flow ratio. TiO2 films were deposited on ITO/PET films and FTO glass substrates. Unipolar pulse or pulse packet modes were used for the sputter depositions. In order to control O2 flow ratio in “transition” and “oxide” regions, oxidation of the target surface was precisely controlled using the feedback system. Sputtering power of each target was kept at 5 kW. Film thickness of TiO2 was 3-10 μm. A sandwiched photovoltaic device was fabricated with N3-sensitized TiO2 photoelectrode and Pt-coated glass as a counter electrode. The deposition rates of both the pulse modes were about 7 nm/min in the “oxide region” and about 40 nm/min in the “transition region”. The maximum value of conversion efficiency in this study was 3.7 % which was obtained in the cell with TiO2 deposited with unipolar pulse mode in the oxide mode on FTO glass substrate. On the other hand, the cell with TiO2 deposited in the pulse packet mode on ITO PET-films performed 1.25 %. Furthermore, we also recognized that TiO2 with high photocatalytic decomposition activity showed high conversion efficiency where TiO2 with poor photocatalytic activity showed poor conversion efficiency.
[1] S. Ohno, Y. Shigesato, et al., Thin Solid Films 445 (2003) 207.
[2] S. Ohno, Y. Shigesato, et al., Jpn. J. Appl. Phys. 43 (2004) 8234.
[3] S. Ohno, Y. Shigesato, et al., Thin Solid Films 496 (2006) 126.