一维有机无机杂化钙钛矿纳米线中的晶界调控及其载流子输运特性研究

Due to the inhomogeneous morphology and random orientation of polycrystals, the transport of charge carriers in hybrid organic-inorganic perovskite polycrystalline film has very complicated path. Till now, the influence of grain boundary on the photo-induced carrier transport is still not well understood. Compared with three-dimensional (3D) structures, one-dimensional (1D) perovskite nanowires are ideal structures to be used in investigating the photo-induced charge transport. Benefiting from the controllability of synthetic methods, as well as the confinement of the charge transport into a 1D nanostructure, the effect of grain boundaries on the photo-induced carrier transport could be amplified. In this project, we proposed a combined solution process and vapour phase conversion method to prepare 1D perovskite nanowires with controlled density of grain boundaries. Meanwhile, the physical mechanism of photo-induced carrier generation, separation and transfer in perovskite nanowires from microscale insights will be unravelled in-situ based on the morphological and structural characterization, as well as spatially resolved optical characterization techniques including scattering-type scanning near-field optical microscope (s-NSOM), confocal photoluminescence/photocurrent mapping techniques. We are aiming to discover the influence of the grain boundaries formed by microcrystals with different orientations on the transport of photo-induced carriers. The success of this project will be beneficial for fabricating high quality perovskite films with optimized grain boundaries and developing higher performance perovskite-based solar cells.

由于有机无机杂化钙钛矿薄膜中晶体形貌不规则，取向较随机，其中载流子输运路径非常复杂，现阶段关于晶界在微观尺度上对钙钛矿光生载流子输运特性的影响机制仍未得到充分解答。相对于三维体相薄膜，一维钙钛矿纳米线是研究其中光生载流子输运特性的理想载体。这是因为一方面可以通过化学方法调控并制备出结构形貌可控的钙钛矿纳米线；另一方面将钙钛矿中光生载流子的输运束缚在一维方向上，减少了多晶界的散射效应，放大了特定晶界对载流子输运的影响。基于此，本项目提出通过湿化学结合气相沉积两步法制备晶界密度可控的钙钛矿纳米线，利用高分辨形貌与结构表征，结合高空间分辨的近场光学显微镜、共聚焦荧光/光电流空间成像等光学表征，从微观尺度原位构建出钙钛矿纳米线中光生载流子产生、分离及输运过程的清晰物理图像，揭示多种晶界形态对钙钛矿载流子输运特性的影响机制。本研究成果将对在钙钛矿成膜过程中优化晶界以构筑高性能太阳能电池具有指导意义。

本项目提出开展钙钛矿纳米结构设计、制备及其载流子输运特性的系统研究。利用近场光学显微镜、荧光/光电流空间成像等高空间分辨率的光学表征技术以及瞬态吸收光谱、荧光寿命光谱等时间分辨的光学表征技术，从微纳尺度上原位构建出钙钛矿材料中光生载流子产生、分离及输运过程的清晰物理图像，揭示出多种晶体形态对钙钛矿材料及其器件结构中载流子输运特性的影响机制。.项目严格按照任务书中规定的研究内容，就项目所涉及的研究任务进行了系统研究。截至目前，项目进展按照任务书中计划执行，研究进度与预期相符。具体而言：.1. 开发新方法制备低维钙钛矿纳米结构，这种钙钛矿纳米结构具有较高的晶体质量以及清晰的表界面结构，可调的晶界密度等，适用于高分辨的光学表征。.2. 采用表面修饰和异质结保护等方法，大幅提高钙钛矿纳米结构的稳定性能。.3. 提出了利用具有高空间分辨率和时间分辨光学表征技术协同揭示钙钛矿中载流子产生、分离、迁移及复合过程的物理图像，从微尺度上阐明了钙钛矿材料及其异质结构中光生载流子的分布与传输规律。.4. 以上述研究基础为指导，构建出系列基于低维钙钛矿结构的高性能光电子器件，包括低电压驱动的宽波段、高响应度光探测器件；具有超快脉冲输出的光纤锁模激光器；高亮度、高外量子效率的LED器件；以及亚波长尺度光场调控的平面透镜等，为下一代微型化、集成化的信息系统集成提供理论和技术的支撑。

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