元素掺杂SnO2透明导电氧化物薄膜中缺陷关联的载流子传输机制研究

Transparent conducting oxide (TCO) films are widely used for optoelectronic device applications such as flat panel displays, touch screens, electrodes in solar cells, and energy-saving windows,etc.,due to its low resistivity, high transparency in the visible range as well as relatively large reflectivity to infrared light. In addition, it is also an indispensible material for developing transparent electronics in the future. Among the advantages of the SnO2-based TCOs are low cost, abundant material resources and non-toxicity, together with wide band gap, high exciton binding energy and good chemical and thermal stability, which makes it becoming a very attractive candidate for coming TCO. In this program,SnO2-based TCO fims with high quality are fabricated by spray pyrolysis, with a view to understanding the defect structures as well as the mechanisms accounting for the electrical and optical properties of the films. By the method of element doping, the carriers in the SnO2-based TCO films are manipulated in a controlled way. On the one hand, the defect structures,its generation and dynamical processes are disclosed by applying multiple technologies such as the synchrotron X-ray diffraction, high-resolution X-ray photoelectron spectroscopy (XPS)and low-temperature photoluminescence (PL) measurements, etc; on the other hand, based on detailed measurements of the temperature behavior of resistivities over a wide temperature range, the dominant charge transport mechanisms and their temperature evolutions are discovered. Thus, the corelation between the defect structures and the conducting mechanisms as well as the optoelectronic properties can be established. All fundamental studies are of very importance not only for understanding the doping mechanisms of SnO2 thin films, but also for realizations of the controllable doping and the optoelectronic device applications in much wider field.

透明导电氧化物(TCO)薄膜具有优良的金属导电性，可见光范围的高透过性以及较高的红外反射率，在平板显示、触摸屏、太阳能电池电极和节能窗口等领域获得广泛的应用，也是开发透明电子器件不可缺少的材料。SnO2基TCO薄膜由于基体材料宽带隙、高激子结合能、优良的热、化学稳定性以及无毒性、原料来源丰富等特点，成为TCO材料的有力候选者。课题以明确SnO2基TCO薄膜的缺陷结构和载流子传输机制为目的，采用超声喷雾热解法制备高品质的SnO2基薄膜。通过元素掺杂工艺实现载流子类型及迁移率的可控性调节。综合运用同步辐射X射线衍射、光致发光谱等技术手段揭示薄膜中缺陷结构、生成及其动态变化，通过大温区内薄膜电阻率的测量揭示薄膜电阻的温度演化规律以及电荷传输机制，建立薄膜中缺陷结构、导电机理和光电性能之间的关联。这些研究对理解SnO2薄膜掺杂机理、实现可控性掺杂、促进它们在光电器件上的应用具有重要价值。

课题以明确SnO2基透明导电薄膜中缺陷关联的载流子传输机制进而掌握薄膜电导调控方法为宗旨，制备多种元素掺杂的SnO2薄膜以及低维结构材料，较为详细的开展了SnO2基透明导电薄膜以及SnO2基低维结构材料中缺陷结构与光电性能之间关联性能的研究；对其中的工艺问题及其物理机制，特别是对材料中掺杂、氧空位、局域应力与电导、透光以及发光等物理性能之间的关系进行了深入的探讨，明确了SnO2基透明导电薄膜中缺陷关联的载流子传输机制和SnO2基低维结构中跟缺陷相关的发光机理，研究结果对理解SnO2薄膜掺杂机理、实现可控性掺杂、促进它们在光电器件上的应用具有重要价值。主要研究成果和创新点有：（1）对Bi掺杂SnO2薄膜（BTO）的微结构特征、基本光电性能以及温度依赖的电阻率变化特征和室温磁电阻效应进行了分析，明确了薄膜中依赖于掺杂量的晶粒尺寸、结晶取向、氧空位等无序结构的变化关系以及此类缺陷结构与载流子传输之间的关联；（2）W掺杂SnO2的电子结构和光学性质理论计算表明掺杂体系具有较高的热稳定性、电导和可见光透射率。对W掺杂SnO2薄膜（WTO）的实验研究揭示出掺杂对薄膜电阻的影响规律，掺杂诱导的薄膜低温下的绝缘体特性起源于电子在低温下的无序效应导致的弱局域化行为，最佳掺杂出现在3 at.%左右。（3）SnO2基低维纳米材料存在缺陷关联的可见光发光特性。氧空位是SnO2纳米粒子中主要的缺陷结构，它的存在会导致带隙变窄和增强的可见光发光，发光强度跟水热反应温度以及激发波长都有关系，以碳球为模板，设计了一种用SnO2基体作为载体、用Sm3+离子作为发光中心的敏化结构的中空球，发现了来自Sm3+离子增强的可见光发光峰，发光峰具有锐利的峰形和可观强度，对提高发光效率和设计新型固体光电发光器件很有价值。.课题目前已经发表11篇论文，其中10篇被SCI收录。参加国内学术会议交流1次，申请相关发明专利2项，授权1项。培养研究生1名，同时对课题组3名青年教师的成长提供支持。