Preparation Of CuO Thin Film And Its Photovaltaic Characteristics

As the ever growing consumption of oil, coal and other traditional energy resources, renewable and clean solar energy is attracting more and more attentions internationally. At present, the hot topics on solar cells research and development focus on two aspects: on the one hand, the improvement of converting efficiency and implementation of large-scale manufacturing as well as reduction on cost; on the other hand, striving for the development of new materials and preparation technologies on thin film cell in order to achieve breakthrough on the research of new type solar cells.CuO is a low cost, safe and stable semiconductor material which is abundant in raw materials and causes no pollution to environment. CuO thin film has an energy band gap of about 1.2-1.9eV, which matches the maximum value of solar spectra and has high theoretical photovoltaic conversion efficiency, so its application in solar cells are more and more importance. However, manufacturing of CuO usually combines with the production of Cu₂O, which affects photovoltaic conversion efficiency, so the prevention of Cu₂O is significant in the fabricate process. Meanwhile, according to many reports: CuO thin film can show either n-type conducting property or p-type conducting property because of different fabricate processes and deposition parameters even when the film is not doped. Then, how to fabricate CuO thin film with different conducting types appears to be an important research issue.In order to probe into the implementation of CuO thin film in solar cells, this paper presents an attempt of fabricating CuO thin film through methods of both magnetron sputtering and thermal evaporation. Researches were done to analyze effects of different parameters on the integrative property, aiming to find effective ways to fabricate CuO thin film with different conducting type and finally to fabricate Cu/p-CuO/n-Si solar cells based on p-type CuO thin film. Firstly the method of magnetron sputtering was used to fabricate CuO thin film and the experimental results showed that all the samples appeared to be n-type conductivity. When the flow ratio of O₂ and Ar is 40sccm/70sccm, n-type CuO thin film with good properties is fabricated under the conditions of unheated substrate and 25-minute sputtering, which had a resistivity of 0.7??cm and a carrier concentration of 3.8×10¹⁶cm^-3. Comparing with magnetron sputtering, thermal evaporation can fabricate both n-type and p-type conducting CuO thin films without being doped. At last, on the basis of former researches, Cu/p-CuO/n-Si solar cells are fabricated. Tests on fabricated Cu/p-CuO/n-Si solar cells were done which proves that the photovoltaic behavior of the cell is mainly caused by p-type CuO thin film. Then, the effects of thin film thickness on the property of solar cells were also analyzed: at optimal condition (with the CuO thickness of 250nm), the solar cell has a short circuit current density of 0.15mA/cm², an open circuit voltage of 0.36V, and a fill factor of 58%.