氧化钒光伏特性及其应用研究

【作者】 卢小铃；

【导师】 王涛；

【作者基本信息】 电子科技大学 ， 光学工程， 2011， 硕士

【摘要】 氧化钒因具有受热辐射后电阻变化的特性,是微测辐射热计用的热敏电阻的理想材料。此外,基于氧化钒光学带隙横跨可见与红外双波段（0.5 eV².24 eV）的理论,提出氧化钒薄膜可以作为光伏探测器光吸收层的想法。通过对半导体光学常数提取方法的总结,确定了氧化钒光学带隙的测定方案。利用椭偏仪测量拟合氧化钒光学带隙:Ⅰ,氧化钒层选用Relaxed-Lorentz模型进行拟合,结合Tauc外推法得到氧化钒光学带隙为0.1 eV;Ⅱ,氧化钒层选用Tauc-Lorentz模型进行拟合,得到两个光学带隙:一个是可见波段,1.9488 ev,解释了氧化钒薄膜在可见波段有吸收这一现象;一个是红外波段,0.1 ev,与Relaxed-Lorentz模型结合Tauc理论得到的光学带隙相符。该结论为氧化钒薄膜应用于光伏器件提供了有力的实验依据。为得到反常氧化钒薄膜,研究了退火温度和退火时间对薄膜方阻值的影响实验结果表明:Ⅰ,随着退火温度的升高,氧化钒薄膜的方阻值呈现下降趋势。这是由于退火温度的升高促进了薄膜中晶粒间界处的缺陷消亡的程度,使得晶粒更加致密,从而导致薄膜方阻值下降。Ⅱ,随着退火时间的升高,氧化钒薄膜的方阻值呈现升高趋势。这是由于氧化钒薄膜随退火时间的增长,氧化程度增强。钒氧化物随着钒价态的升高,方阻值呈上升趋势。采用反应磁控溅射方法在K9玻璃衬底上制备氧化钒薄膜并对其进行特定条件的退火处理。室温时,通过KEYTHLEY4200半导体特征测试系统,选用二端测试模型测得,300℃退火180s的氧化钒薄膜在可见光照情况下呈现反常光伏效应。利用X射线光电子能谱（XPS）对薄膜进行分析,结果表明,光伏效应氧化钒薄膜表层形成了一层以V⁵⁺为主,同时含有V⁴⁺的混合相氧化钒薄膜（VOX）活性层,该层体现出光伏效应。通过紫外可见分光光度计UV1700测得该薄膜在可见光波段380 nm¹100 nm有明显的光吸收,并利用“Dember”理论和场制表面电压理论对其光生电压的机制给出分析。基于氧化钒在可见和红外双波段的光吸收性质,提出将其应用到MSM-PD光伏探测器件中的想法,并就氧化钒薄膜应用于光伏器件提出整体设计思路和制备工艺。本文结论对于氧化钒应用到光伏探测器中的可行性及其应用前景具有相当的指导意义。更多还原

【Abstract】 The enhanced characteristic, that the resistance changes while being radiated, makes vanadium oxide widely used optical material. Besides, it is supposed that vanadium oxide could be the absorption layer applied into photovoltaic devices, due to the fact that its optical band gap covers from infrared to visible light region.By summarizing the general methods of obtaining optical parameters of semiconductor, the concrete measurement design for optical band gap of vanadium oxide was determined by using Spectroscopic Ellipsometry: I, combining with Tauc theory, Relaxed-Lorentz model was applied for fixing vanadium oxide layer and the measurement result reveals that the optical band gap of vanadium oxide is 0.1ev. II. By applied Tauc-Lorentz model for fixing vanadium oxide layer, the results tell that there are two band gaps, one is 1.9488ev which can give the reasonable explanation that vanadium oxide layer’s absorption in the visible light region; another is 0.1ev that coincides with the result of the former measurement. The conclusion of the optical band gap of vanadium oxide provides a powerful proof for its application in the photovoltaic devices.In order to achieve anomalous photovoltaic effect vanadium oxide thin film, the influence of annealing treatments’parameters, annealing temperature and annealing time, were extensively studied. The results reveal the sheet resistance decrease with the annealing temperature increases and the annealing time decrease respectively. Due to the fact that the defects between the interfaces of crystallites disappear with the temperature increases and the thin film becomes denser, the sheet resistance of vanadium oxide decreases. Due to the fact that a small amount of the oxygen was remain in annealing furnace, with the annealing time increase, the degree of oxidation of vanadium element increase, inducing the sheet resistance increase.Oxide vanadium thin films were deposited on K9 glass substrates by reactive magnetron sputtering method. After being annealed under special conditions, photovoltaic effect of oxide vanadium thin film was observed by KEYTHLEY 4200 semiconductor characterization system at room temperature when the film is exposed on visible light environment. We have investigated the oxide vanadium thin films by X-ray photoelectron spectroscopy （XPS） and the results show that the surface of the photovoltaic oxide vanadium thin film was an active layer which contained V⁵⁺ in majority and V⁴⁺ in minority. The photovoltaic mechanism was studied and explained by UV1700 and the theory of“Dember”effect and electric field induced surface voltage.Due to the property that oxide vanadium thin films could absorb visible and infrared light, a creative thought was proposed that oxide vanadium thin films could apply to photovoltaic devices as light absorb layer. In this paper, the device structure and manufacture steps were explicated designed.The conclusion provides a forceful evidence for oxide vanadium thin film’s application in the photovoltaic devices.更多还原