非化学计量比F掺杂SnO2薄膜的缺陷行为及光致发光机理

Due to wider band gap (3.6 eV), higher exciton binding energy (130 meV) and better stability, SnO2-based film will be a member of the promising luminescent materials. At present, the research on F-doped SnO2 (FTO) film mainly focused on its transparency, conductivity and gas sensitivity. However, the photoluminescence (PL) properties of FTO film have not been investigated and evaluated in detail and in depth, and there have been disputes on the PL mechenism, which restricts its applications in optoelectronic devices. In this project, nonstoichiometric FTO film will be prepared by spray pyrolysis, the microstructural defects will be modulated effectively by the changes of parameters, such as F-doping content and those during the post-heat treatment process. The band structure of FTO crystalline grain will be modified by the intermediate level formed by defects, which can break the dipole-forbidden band-gap transition rule of SnO2. The relationship between surface structure, internal defects and PL properties will be established. The defect behaviors will be discussed deeply, and the PL mechanism will be investigated. This work will provide the theoretical and experimental foundation for expanding the potential applications of FTO films in the field of the optoelectronic devices.

宽带隙（3.6 eV）、高激子结合能（130 meV）且稳定性良好的SnO2基薄膜是一种非常有前途的发光材料。目前关于掺F的SnO2薄膜（FTO）的研究主要集中于透明性、导电性和气敏性，而其光致发光性能尚未得到详细深入的研究，其光致发光机理仍存在争议，制约了其在光电子器件中的应用。本项目拟采用喷雾热解法制备非化学计量比FTO薄膜，通过改变F掺杂量及热处理工艺等参数，调控非化学计量比FTO薄膜的内部微观结构缺陷，通过缺陷形成的中间能级对FTO晶体的能带结构进行修饰，打破SnO2带边量子态的偶极禁阻本性，建立FTO薄膜表面结构和内部缺陷与发光性能之间的联系，深入探讨缺陷效应，揭示FTO薄膜光致发光性能的物理机制。本项目的完成为拓展FTO薄膜在光学器件上的潜在应用提供理论依据和数据支撑。

宽带隙（3.6 eV）、高激子结合能（130 meV）且稳定性良好的SnO2基薄膜是一种非常有前途的发光材料，而F掺杂SnO2薄膜（FTO）光致发光性能尚未得到详细深入的研究，其光致发光机理仍存在争议，制约了其在光电子器件中的应用。本项目通过改变F掺杂量、溶剂及热处理工艺等参数，制备了非化学计量比FTO粉体及薄膜，研究各个参数对微观结构的影响，探索了微结构中的缺陷形式及状态，并建立了掺杂 F、氧空位等结构缺陷与发光性能之间的联系。重要结果为，FTO均为四方金红石结构，且存在不同的择优取向。由于F的掺入，SnO2晶格中存在三种状态的氧，SnO2带隙中出现了三种氧空位和F离子形成的中间能级，电子在导带、价带及中间能级之间的跃迁会产生不同波长的发光，表面态、结构缺陷等相关的缺陷形成的发光中心也会在室温产生发光。同时利用第一性原理计算了微观结构，相对于单Nb和F掺杂，Nb和F共掺杂的SnO2有更小的结构畸变。Nb（4d）和F（2p）电子共同作用使SnO2导带离散度增加，且导带下移和价带上移同时发生，降低了电子跃迁所需的能量。本项目的完成为拓展FTO薄膜在光学器件上的潜在应用提供理论依据和数据支撑。