Synthesis And Photoelectric Properties Of ZnO/Cu₂O Nano-heterojunction Arrays

The application of ZnO semiconductor material has been widely researched recently. However, as the shortage of crystal defect of ZnO and its self-compensation effect, most manufactured ZnO nanowire arrays usually shows the characteristic of n-type material. Many scientists work on covering the shortage of p-type ZnO, but it has not reached the requirement in practice. ZnO is no toxic, harmless, easily produced and has good electric conductivity, which is a kind of good n-style nanowire arrays in the field of solar cells and other optoelectronic devices. Thus, scientists are looking for a kind of p-type semiconductor material whose lattice matching is fit for n-type ZnO and can be applied to optoelectronic device and other kinds of nano-electronic devices. Therefore, the key point of ZnO application is to find a p-type semiconductor material which reaches the requirement of material and electronic characteristic, combing such p-type semiconductor material to match with ZnO so that can perform a stable p-n semiconductor heterojunction. Cu₂ O is a relatively stable p-type semiconductor material which is also no-toxic, harmless and easily to be produced. Thus, Cu₂ O is a good material to produce heterojunction with n-type ZnO.This research is based on hydrothermal synthesis method aligned n-type ZnO. Nanowire arrays of n-type ZnO are coated with deposited p-type Cu₂ O by using electrochemical deposition method, producing ZnO/Cu₂ O core-shell nanowire arrys heterojunction. Then the effect of preparation condition and preparation parameters on ZnO/Cu₂ O core-shell nanowire arrys heterojunction is analyzed. The result of this research makes a contribution to developing and exploring novel solar cell and photoelectric devices by using ZnO.The main research contents are as follows:Firstly, apply a magnetron sputtering method to sputter a layer of ZnO seed layers about 20 nm. Using hydrothermal synthesis method to produce ZnO nanowire arrays based on the above layer. The condition of hydrothermal synthesis method is high pressure, 95 centigrade, 25 Mm of molarity, and 1:1 molar ratio of Zn（CH3COO）2·2H2O:C6H12N. Electrodeposited nanowire arrays based on the cell layer which growth uniformly and have a stable hexagonal wurtzite structure. Then describe the characteristics by SEM、XRD and PL between different temperature, molar ratio,reaction time and the thickness of the ZnO cell layer.Secondly, by using of an electrochemical workstation and three electrode deposition method, a layer of Cu₂ O semiconductor core-shell cladding layer was deposited on the synthesized aligned ZnO semiconductor nanowire arrays. In the process of electrodeposition, the best testing parameters for the ZnO/Cu₂ O photoelectric conversion prototype devices are as follows: the test temperature is 25 centigrade, lactic acid is 3 mol/L, the molar concentration of copper sulfate is 0.4 mol/L for the electrolyte, ph=11, and the applied deposited voltage is 0.4v with the time is 30 min. The ZnO/Cu₂ O heterojunction arrays with better coated features are prepared. And the microstructure, morphology, photoluminesence properties of the ZnO/Cu₂ O heterojunction arrays were analyzed by using of field emission scanning electron microscopy（SEM）、XRD and other equipments.Thirdly, the simple ZnO/Cu₂ O photoelectric conversion prototype devices were prepared with the synthesized ZnO/Cu₂ O heterojunction arrays. And the photoelectric characteristics of the ZnO/Cu₂ O photoelectric conversion devices were analyzed and tested under a 80 w/cm2 xenon lamp was used as a sunlight simulation source, the keithley 4200-SCS semiconductor features analysis system was used as testing system for IV photoelectric characteristics. The impact of the preparation parameters, growth structure, the thickness of the ZnO cell layer, and deposition time on the photoelectric device preparation were analyzed. In the end, the IV characteristics research and light response test of n-ZnO/p-Cu₂ O junction photoelectric conversion devices found the best deposition time and applied deposition voltage are 30 minutes and 0.4V, respectively. Under this prepared condition, of the ZnO/Cu₂ O junction device present the best photoelectric conversion characteristic.