Preparation Of Cu₂O Films By Eletrochemical Deposition And Study Of The Photoresponse Properties

Cuprous oxide?Cu₂O?is an important p-type semiconductor with the narrow band gap of1.9 2.5 eV.Cu₂ O is considered as a promising material for solar cells,photodetectors,and catalysis because of the excellent optical and electrical properties.Electrochemical deposition method is widely used for the preparation of Cu₂ O films,which is a simple and low cost technique to deposit films.In the process of electrochemical deposition,the conditions such as substrates,composition of the electrolyte,deposition time and temperature,deposition current or voltage can affect the morphology,crystalline quality and optical and electrical properties of Cu₂ O films.In this paper,Cu₂ O films were fabricated on different substrates by electrodeposition using the electrolyte with different pH values and deposition current.The influence of deposition conditions on the morphology,crystalline structure and optical-electronic properties of Cu₂ O films were investigated.The main research contents and results are as follows:1.Cu₂ O films with different morphology and crystalline quality were fabricated on FTO and ZnO thin film substrates by electrochemical cathodic reduction using the electrolyte with different pH values?9.5,10.5,and 12.5?.The crystalline quality exhibits nonlinear increase-decrease with the electrolyte pH increase.The Cu₂ O film with good crystalline quality was deposited in the electrolyte with 10.5 pH and Fermi level of the film is close the top of the valence band.The Cu₂ O films deposited on the FTO substrates are polycrystalline with a preferred orientation along the?111?plane,and the intensity of the?111?diffraction peak increases first and then decreases with the increase of pH value.Whereas a transition of the preferred orientation from?100?to?111?occurs for Cu₂ O films on ZnO thin film substrates as electrolyte pH increases.The XRD results are consistent with the morphology of Cu₂ O films.All the PL spectra of the films present similar characteristics: one green emission band is attributed to inter-band transitions,whereas the red emission band is associated with the defect states.Compared to Cu₂ O films on FTO substrates,the PL spectra are relatively weak for the films deposited on ZnO thin film substrates.The Cu₂ O films deposited on ZnO thin film substrates show a photovoltaic effect under the illumination and show highly sensitive to the visible light illumination at zero bias voltage,with excellent stability and reproducibility.The larger photocurrent of the Cu₂ O film deposited in the electrolyte with10.5 pH is attributed to the good crystal quality of the Cu₂ O films and strong built-in electric field of Cu₂O/ZnO interface.2.One-dimensional materials exhibit good directional charge transport properties.Cu₂O/ZnO NRs heterojunctions.were formed by the Cu₂ O films deposited on ZnO nanorod arrays?NRs?.The photoresponse of the heterojunctions were investigated.The diameter size and crystal quality of ZnO NRs can be regulated by ZnO seed layers.ZnO NRs with wellcrystal quality were obtained on the seed layers of 0.5% Al-doped ZnO?named as AZO 0.5%?.Cu₂O/ZnO NRs with AZO 0.5% seed layer exhibits good photoresponse properties.Although Cu₂O/ZnO NRs and Cu₂O/ZnO film heterojunctions both show the self-powered photoresponse properties,the photocurrent and the responsivity of Cu₂O/ZnO NRs are larger than that of Cu₂O/ZnO film heterojunction.The phenomenon can be attributed to the good directional charge transport properties of ZnO NRs,reduced the interface recombine and increase of carrier lifetime.3.Cu₂ O films were deposited under the different deposition current?3-12 mA?.The influence of the deposition current on the crystal quality,morphologies and photocatalytic properties of Cu₂ O films were investigated.The results revealed that Cu₂ O deposited under9 mA deposition current exhibit good crystal quality and absorption capacity in the visible region.For the Cu₂ O film deposited under 9 mA deposition current photocatalyst activity for decomposition of methylene blue is much stronger than that of other Cu₂ O films.