| Cu2O is important metal-oxide p-type semiconductors, which has promising applications in solar energy conversion, catalysis, gas sensor, and so forth. Such as Cu2O is a potential material for low-cost photovoltaic power generation because it has a theoretical solar cell conversion efficiency of 18 % . CuO is an important oxide of transition metal with many practical applications, such as it is the basis of several high-Tc superconductors and materials with giant magnetore-sistance, and is also used as catalysts, pigment, p-type semiconductor, gas sensors, solar cells, magnetic storage media and cathode materials. The development of specific morphology and structure has attracted significant interest due to the resulting novel structures, properties, and applications. Present research is geared towards Schottky barrier and heterojunction solar cells of Cu2O. Both frontwall (Cu/Cu2O) and backwall (Cu2O/Cu) Schottky barrier solar cells have been studied with promising results. There are some investigations on the syntheses of Cu2O and CuO powders with varied morphologies or with hollow structures and complex hierarchy, such as wires, cubes, pyramids, rods, hollow microspheres, flowers octahedrons, hollow Cu2O octahedral, hollow Cu2O nanocube and hollow Cu2O sphere with more one shell. The Cu/ Cu2O structure have been prepared by electrodeposition and thermal oxidation. However, Cu/Cu2O core/multi-shelled truncated octahedron and Cu/Cu2O core/multi-shelled octahedron have not yet been reported.It is found that the microemulsion system, water content, ligand, reaction temperature, reaction time, template and so forth play important roles in the formation of the novel morphology and structure besides the crystal habit of Cu2O. Typically, varying the time of oxidation of copper (Cu) colloids, can obtain Cu2O nanoparticles of different shapes in the presence of iodine ion; by adjusting the concentration of CTAB (cetyltrimethylammnium bromide) as template whilst keeping the other conditions constant, Xu and co-workers control the structure of the hollow spheres (the number of shells) simply; varying the concentrations of glucose and the amine, can obtain various Cu2O morphologies such as hexapods, stars, octahedral, and cubes; modifying the composition of the source materials can drastically change the morphology of the grown micro-/nanostructure. However, most of the above-mentioned Cu2O crystals not belong to the structural change. It is meaningful to investigate the structural change process of as-prepared microcrystal, which can provide important information to the fields of crystal growth and design and structure-controlled synthesis of inorganic building blocks. To study the growth history of Cu2O and/or Cu microcrystal, we control the aging time, following the reduction of TEA concentration, which makes it possible to arrest the different structural Cu2O and/or Cu microcrystal in different stages of their growth.The surface photovoltage spectroscopy (SPS) is contactless and non-destructive, it can be applied not only to clean surfaces, but also to real ones, in practically any ambient. With the aid of an external electric field, the SPS technique can provide more information about the properties of the semiconductor surface, because when a direct current electric field is applied to the sample, the mobile and/or diffusive distance of photoexcited charge carriers can be varied. The surface photovoltage can provide direct information of charge separation due to the fact that it can be split up in two contributions: total amount of charge and distance between the centers of charge of the positive and negative carriers. After the sample receives the photons of appropriate energy, the net surface charge change, indicating that the SPS signals is generated. The surface photovoltage is inherently sensitive to the buried interfaces just as it is sensitive to the external surface. In general, the SPS signals of the buried interfaces and the external surface have to do with a reduced photon flux arriving at the buried interfaces due to partial or complete absorption of some light on the surface; has to do with the induced traps effecting on the transfer of photoexcited carriers and so forth. Therefore, we can prove the surface oxidation of semiconductors and distinguish the main contribution to the photovoltage signal from the buried interfaces or the external surface in the different photovoltage respond regions.SPS has found significant uses: in studying the semiconductor band gap energy , type, (surface and bulk) defect states, surface electronic structure and so on;in studying the metal-semiconductor interfaces, multilayer structures; in studying the impact of adsorption processes in a gaseous ambient and the effects of chemical reactions between semiconductor and gas,such investigations were the oxidation of, or oxygen adsorption on, Ge, Si, GaAs, CdS, CdSe, ZnO, and more. A number of studies have addressed the leve alignment at the interface between organic layers and metal or semiconductor substrates. This is an important issue for understanding the charge carrier transport across the interface. Especially ultraviolet photoemission spectroscopy (UPS) was used to study these interface properties. There are only a few experimental techniques allowing to obtain information about electronic states in ultrathin metal oxides. Photovoltage measurements have the advantages to be contactless and to give information about the type of states. This makes Photovoltage measurements more universal than other techniques such as photoelectron spectroscopy or internal electron photoemission.The research on Copper oxide material mainly follows hereinafter aspeacts:1. Octahedron Cu2O samples with different size have been synthesized, which were studied by means of surface photovoltage spectroscopy (SPS), electric field induced SPS (EFISPS), transient photovoltage (PV) and other analytical tools to investigate the stability of Octahedron Cu2O in air and the surface oxidation effect on the transfer of photoexcited electrons and holes. 2.CuO nanoparticles with 45.2nm, 57.4nm and 68.4nm size have been synthesized by a hydrothermal method using the CuCl2 ? 2H2O and NaOH solution as the reaction materials. Experiment shows that CuO nanoparticles are not pure when the NaOH concentration is relative small, and the size of CuO nanoparticles increases as the NaOH concentration increasing. In addition, we research on photovoltage property of CuO nanoparticles.3. CuO/Cu2O microcrystal is obtained by varying the aging time and the relative volume ratio of TEA and distilled water. In addition, we made a systems photovoltage study for CuO/Cu2O microcrystal with transient and spectral photovoltage techniques. Experiments show that the aging time and the relative volume ratio of TEA and distilled water affect the shape and component of CuO/Cu2O microcrystal; the aging time of CuO/Cu2O microcrystal would be controlled between 50 min and 2 h. For CuO/Cu2O microcrystal, a visible acromion appears in the shortwave region of the photovoltage spectral; as the increasing amount of CuO, main photovoltage responding region gradually red-shift and photovoltage signal gradually decrease. By comparing the photovoltage spectral under electric field with no electric field, it founds that the main photovoltage responding peaks of CuO/Cu2O microcrystal blue shift at least 100nm. In addition, the blue shift on the EFISPS curve due to surface CuO, gives information about the surface photovoltage signal: in the light wavelength region from 484.6 nm to 296.3 nm, should be dominated by the bulk Cu2O with wide-gap; whereas from 776.2 nm to 484.6 nm, should be dominated by CuO with narrow-gap on the surface.4. The Cu2O octahedron, Cu/Cu2O core/multi-shelled truncated octahedron and Cu/Cu2O core/multi-shelled octahedron microcrystal can be easily obtained by varying the aging time with the assistance of TEA (triethanolamine). The possible mechanism for the formation and evolution of the different particle shapes are proposed. The TEA not only as the reducing agent but also as template is believed to play a key role in the shape and structure transformation process. Aging time controls and use of TEA as template are essential for the formation of core/multi-shelled structures and shape evolution of the obtained particles. Photovoltage signals, which are strongly affected by the Cu amount depending on the aging time, are observed at Cu/Cu2O core/multi-shelled structures with transient and spectral photovoltage (PV) techniques.
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