Paper SS-TuP11
Photovoltaic Property of Cu₂O/Cu/TiO₂ Thin Films Prepared by Reactive Magnetron Sputtering

Tuesday, October 30, 2012, 6:00 pm, Room Central Hall

Recently, TiO₂ is considered as one of attractive materials. Since the photoinduced decomposition of water on the T iO₂electrode was discovered, the photocatalysis based on semiconductor property has attracted extensive interest. TiO₂ is an n-type semiconductor with a band gap energy of 3.0 - 3.2 eV and is well known as a versatile material. From the view of solar cells TiO₂ is applied in development of dye-sensitized solar cells (DSSCs) or quasi-one-dimensional TiO₂ nanotube structure. On the other hand Cu₂O is a p-type semiconductor with a direct band gap of 2.0 eV and is a promising material on solar cell applications because of its nontoxicity, low cost and high absorption coefficient in the visible region. In this study, the photovoltaic property of p-Cu₂O/n-TiO₂ solar cells which was prepared by magnetron sputtering was investigated. Furthermore Cu buffer layer between TiO₂ and Cu₂O was used to obtain high efficiency.

Cu₂O/Cu/TiO₂ thin films with p-n heterojunction were fabricated by reactive magnetron sputtering. Firstly, glasses (Corning#1737) and ITO-film coated glasses as a substrate were ultrasonically cleaned by an acetone rinse. The TiO₂ thin film was deposited on glass substrates using pure metallic titanium (99.99%) as a sputtering target material in an oxygen gas atmosphere. The flow rates of a sputtering argon gas and an oxygen gas were 20 sccm and 1.5 sccm, respectively. Secondly, the Cu thin film was deposited on the TiO₂ thin film using pure metallic copper (99.99%) as a sputtering target material. Thirdly, the Cu₂O thin film was deposited on the Cu/TiO₂ thin film. The flow rates of a sputtering argon gas and an oxygen gas were 15 sccm and 10 sccm, respectively. Each thickness of the TiO₂ and Cu₂O layer was about 100 nm and 200 nm. Composition and microstructure of these films were investigated by the X-ray photoelectron spectroscopy and the X-ray diffraction. Transmittance of the TiO₂ and Cu₂O thin film was measured by a spectrophotometer. The photovoltaic property was evaluated by measuring the current–voltage curve.

The Cu₂O/Cu/TiO₂ thin films with p-n heterojunction were successfully fabricated by reactive magnetron sputtering. The XRD diffraction pattern of TiO₂ layers deposited at an oxygen flow rate of 1.5 sccm showed a mixture structure. The open voltage of Cu₂O/Cu/TiO₂ thin films showed a higher value under artificial sun light than Cu₂O/TiO₂ thin films. It was confirmed that the buffer layer of Cu improved the photovoltaic property of Cu₂O/TiO₂ thin films.