【作者】 赵锐；

【导师】 贺高红； Yulin Deng；

【作者基本信息】 大连理工大学 ， 化学工程与技术， 2013， 博士

【摘要】 为了适应整流二极管和光电转换器件等电子元器件轻薄化、柔性化等发展趋势,电子材料的研制成为材料领域研究的热点之一。基于材料的物理和化学特性,辅以功能实现方式和器件结构的设计,是构建新型电子元器件的基本思路,可解决其目前面临的问题以满足未来的发展要求。以此为主题,本论文分为两部分,第一部分利用两种液相法设计并制备了具有不同禁带宽度的氧化锌材料,用于组装异质结整流二极管。第二部分制备了银基电解质材料,利用电解质中银碘离子对的电化学和沉淀特性,在PEG环境中实现了整流性能,使离子二极管的构建和运行过程摆脱了水体系电解液,实现了该类器件的全固态化和柔性化。进一步将银碘体系材料的电化学性质扩展到碘化银光电器件的设计,提高了该类器件的运行时间。氧化锌是一种重要的半导体材料,其电学性能与禁带宽度密切相关。不同的生长环境可以使氧化锌具有不同的杂质或缺陷状态,造成禁带宽度间的差异。乳化液膜法和液相直接沉淀法是同属于沉淀反应机理的两种液相制备方法,但乳化液膜法因油水界面的存在,不同于液相直接沉淀法。论文根据乳液界面对晶核生长过程的控制作用,制备了禁带宽度为2.93eV的氧化锌颗粒,利用SEM和XRD研究了颗粒在内水相液滴中的生长过程,证明油水界面的存在限制了颗粒的尺寸,且内水相液滴从3μm增大到5gm时,颗粒形貌由棒状转变成片状。利用XRD和界面张力测试证实油水界面上的表面活性剂会吸附于颗粒的表面,使制得的氧化锌颗粒存在杂质或缺陷。该氧化锌颗粒和液相直接沉淀法制备的氧化锌颗粒具有相近的晶体结构,但禁带宽度相差0.13eV,可形成异质结,将其组装成三明治结构的二极管,具有整流能力。无机半导体二极管的发展已经接近其物理极限,因此以离子二极管作为其替换或补充的下一代整流器件具有极大的研究价值。但离子二极管强烈依赖水体系电解液,水的易挥发性和高温不稳定性限制了其应用范围。为解决此问题,选用具有解离能力和离子传导能力且物化性质稳定的聚乙二醇(PEG400)为电解质溶剂,提出利用易电解且相互沉淀的离子对实现整流功能的新方法,将AgN03电解质和LiI电解质分置于多孔分隔膜两侧组装成三明治结构离子二极管。在正向偏压下,两侧的银离子和碘离子相背运动到各自相邻电极上发生电解反应产生电流,器件实现导通。电场方向反转后,银离子和碘离子将转换为相向运动,因在接触界面处发生沉淀反应而无法到达对电极发生对称的电解反应,而电极上惰性的NO3-和Li+在低电压下难以电解,此时器件中无电流产生。囚此,器件实现整流功能,开启电压为0.3V,击穿电压为-2.7V,偏压为1.5V时的整流比为40,高于目前大部分离子整流器件,连续运行300个周期后仍具有整流能力。这种利用液态电解质实现整流功能的方法可用于多种无机化合物或者有机化合物的组合。PEG的固液状态可根据其分子量大小进行调节,利用这种性质,可以实现电解质的固态化。高分子量PEG强度较差,难以自支撑,利用纸纤维为支撑材料可以解决这一问题,实现电解质材料的柔性化。基于此,论文利用PEG20000为电解质环境、纸纤维为支撑材料制备出AgN03和KI的柔性固态电解质材料,并组装成离子二极管。这种二极管在±1V下的整流比为46,可承受大幅弯曲(弯曲半径15mm),且耐受800次以上的连续弯曲。电解质材料的固态化可以减弱离子的扩散,使器件的静置寿命达32天。银-碘材料间的电化学性质可以扩展到光电转换功能的实现。针对该器件因碘化银的光化学反应不可逆而造成的运行寿命短(数分钟)的问题,结合银碘化学电池和染料敏化太阳能电池结构的设计方法,以沉积了碘化银膜的导电玻璃为光电极,铂电极为对电极,I-/13-的碳酸丙烯酯溶液为电解液,在两电极间加入遮光板构建了碘化银光电转换器件。利用碘化银在光照下生成单质银的能力,使器件转变成银碘化学电池体系输出电流,实现光电转换,同时单质银在碘离子的存在下被氧化,实现碘化银的再生。理论上器件在运行过程中不存在反应物的消耗。使用氙灯在100mW/cm2的光强度下照射,器件在长达47小时的连续运行过程中光电效应始终存在,对光开关的阶跃响应时间约1.2秒,光电流密度约0.7μA/cm2。遮光板防止了游离的碘化银颗粒在对电极上发生光化学反应而造成的内部短路,相比于未使用遮光板的器件,光电流可提高17倍。铂对电极对I3-反应具有催化能力,使光电流为氧化钢锡(ITO)对电极器件的7倍,而光开关响应时间仅为其1/6。器件输出的光电流大小与入射光强和波长相关,具有制作光检测器的潜力。更多还原

【Abstract】 Design and preparation of novel electronic materials have attracted great interest to meet the demands of flexibility and miniaturization of rectifier diodes and photoelectric devices. It can be achieved through designing the structure of devices based on the physical and chemical properties of materials. This thesis was separated into two parts for fabricating novel rectifier and photoelectric devices. In the first part, ZnO particles with different band gap were prepared via two kinds of liquid phase methods (LP) and further fabricated into heterojunction diode. In the second part, silver-based electrolyte materials were prepared and fabricated into non-water ionic diode. Based on the electrochemical properties and precipitation reaction of Ag-I system, rectification behavior was achieved in the PEG electrolyte. At last, the electrochemical properties of Ag-I system were employed to design AgI photoelectric devices with a long-time running.ZnO is a kind of important semiconductor for preparing electric components, of which the electric property strongly depends on the band gap. Emulsion liquid membrane (ELM) method and direct precipitation method (DP) are similar LP methods based on precipitation reaction but some difference due to the influence of W/O interface of the emulsion. Herein, ZnO particles with band gap of2.93eV were prepared by ELM method where the nucleation process and the morphology and property of the particles are controlled by the nature of W/O interface of the emulsion. The effect of W/O interface properties on the morphology and size of the ZnO particles were proved by investigating the growth mechanism of the particles with SEM and XRD. The morphology of the particles varied from rod-like to sheet-like when the size of internal water droplets was increased from3to5μm. It was further demonstrated that the surfactant tended to be absorpted on the particles by XRD and interfacial tensiometer studies, which could induce the impurities and defects into the material. The ZnO particles prepared by ELM method exhibit a similar crystal structure to those synthesized by DP method but a different band gap of0.13eV, which fits the requirement of heterojunction formation. Therefore, a ZnO heterojunction diode with a sandwich structure was fabricated with the ZnO prepared by the two methods and exhibited rectifying behavior.The performance of inorganic semiconductor diode is approaching the limits of the physical peroperty of materials. Ionic diodes as the next generation rectifier are expected to replace or extend the function of inorganic semiconductor diode, and have attracted a great deal of attention. Ionic diodes strongly depend on water-based electrolyte which is volatile and instable at high temperature. Therefore, non-water ionic diodes need to be studied for application. In this work, PEG400was chosen as electrolyte host due to its stable property and the ability of ionic dissociation and transport. But its high viscosity caused all reported methods based on nanofluidic channels etc. can not be employed to prepare ionic diode. Therefore, a novel method was demonstrated using Ag+-I-ion pair which had a low electrolysis voltage and could precipitate with each other. The ionic diode was fabricated into sandwich structure, in which AgNO3/PEG and LiI/PEG electrolyte were separated by porous membrane. Under forward bias voltage, Ag+and I-moved to the electrode on their side respectively, and electrolytic reaction occurred to generate current. In this case, the device was conductive. Under backward bias voltage, Ag+and I-moved to their counter electrode and were blocked due to precipitation. Meanwhile, the electrolytic reaction of NO3-and Li+counter ions pair could not happen because they needed a very high applied voltage. The device was unconductive at that time. Therefore, the ionic diode exhibited recitification function. The open-circuit voltage is0.3V. Breakdown voltage is-2.7V. And recitification ratio is40under AC voltage between±1.5V, which is higher than most of reported ionic diode. The device could work more than300cycles. The principle of this study is general and can be extended to the fabrication of ionic diodes with different inorganic or organic salt.The appearance of PEG from liquid to solid state could be achieved through increasing their molecular weight. That could be employed to prepare solid state ionic diode. Herein, flexible solid state electrolyte material was prepared using PEG20000as electrolyte host and paper fibers as supporter because PEG20000had poor strength for self-supporting. The flexible paper-based solid state ionic diode was fabricated by AgNO3and KI electrolyte materials. Its recitification ratio is46under AC voltage between±1V. The devices exhibited good flexibility and showed stable rectifying behavior after more than800bending cycles. Its standing stabilitytime was32days. Adding10wt%PC as plasticizer could increase the forward current by3times but decreased the standing stabilitytime to less than4days. The results showed that there was a trade-off between rectifying performance and stability.The electrochemical properties of Ag-I system could be extended to prepare AgI photoelectric device for improving its stability (several minutes reported). A novel method was demonstrated to prepare long-time running AgI photoelectric device. The structure of dye-sensitived solar cell and Ag-I2chemical battery enlightened us to fabricate the device to be sandwich structure using ITO glass deposited with AgI film as photoelectrode, Pt as counter electrode and I/I3-/PC solution as electrolyte. A light shield was added between two electrodes for avoiding incident light arriving at the counter electrode. Photochemical reaction could decomposite Agl to be element Ag and I2on the photoelectrode under illumination. Oxidation of element Ag with I and reduction of I2occurred to make the device to be Ag-I chemical battery and outputed current. Agl regenerated due to the oxidation reaction in this process. Theoretically, the device could be operated for a long time without reactants consumption. The prepared device could output0.7μA/cm2current density with a rapid photoelectric response (1.2s) and kept the performance after47hours continuous illumination. Light shield avoided short-circuit caused by photochemical reaction of AgI at the counter electrode. Comparing the device without light shield, the current was higher by17times. Pt counter electrode could increase the current by7times and accelerate the photoelectric response rate due to its catalytic property. The device could generate different current density under various wavelength or intensity of incident light. Therefore, it exhibits the potential to prepare photodetector.更多还原