Paper TF-ThP20
The Influence of ZnO Layers for Photovoltage of Cu₂O/ZnO/TiO₂ Thin Films Prepared by Reactive Sputtering

Thursday, October 25, 2018, 6:00 pm, Room Hall B

As one of solution methods of the power shortage and global warming, a renewable energy such as solar cells is desired. In addition the high purity silicon that is the main raw material for solar cells is insufficient worldwide, and so new solar cells without silicon that are able to be replaced to silicon-based solar cells have been required. Practical application of oxide-based thin film solar cells is expected in reduction of the energy cost or the environmental load.

Generally a typical oxide-based thin film solar cell is known as a wet dye-sensitized solar cell composed of an electrolyte, an electrode of a titanium oxide and a sensitizing dye. Recently a solid-state dye-sensitized solar cell which uses metal oxides instead of an electrolyte has been studied. In our previous study on Cu₂O/TiO₂ solid-state dye-sensitized solar cells, the main problem was Cu diffusion from a Cu₂O layer to a TiO₂ layer. Because the diffusion of Cu to a titanium oxide layer induces the collapse of p-n junction, various materials as an intermediate layer between Cu₂O and TiO₂ have been attempted.

The ZnO layer used in this study has characteristics of a transparent oxide semiconductor, a low electrical resistivity or an n-type semiconductor. Especially the ZnO layer show a lower value about an electrical resistivity than the NiO layer or the TaON layer which had been used in the previous study.

Cu₂O/ZnO/TiO₂ solar cells were fabricated by reactive magnetron sputtering. As substrates, the EAGLE XG glass and the ITO-film coated glass were ultrasonically cleaned by acetone. The oxide layers were deposited on those substrates by using pure metals as a sputtering target material in an oxygen gas atmosphere. The flow rate of an argon gas for sputtering was kept at 15 sccm of Cu₂O, and at 20 sccm of TiO₂ and ZnO. The flow rate of an oxygen gas for sputtering was kept at 1.5 sccm of TiO₂, and at 10 sccm of Cu₂O and ZnO A thickness of a TiO₂ and a Cu₂O layer was kept at 200 nm, while a thickness of the ZnO layer was changed from 2 nm to 50 nm. Cu₂O/ZnO/TiO₂ solar cells were successfully fabricated by reactive magnetron sputtering. The investigation of Cu₂O/ZnO/TiO₂ solar cells were carried out by an x-ray diffraction, a spectrophotometer and a field emission Auger microprobe.