Two-dimensional (2D) van der Waals materials have attracted tremendous attention due to their versatile physical properties and flexible manipulation approaches. Among the various types of van der Waals materials, α-In2Se3 is remarkable for its intrinsic 2D ferroelectricity and high-performance opto-electronic properties. However, the study of the α-In2Se3 system in terahertz (THz) radiation is scarce, although it is promising for electrically controlled THz field manipulation. We investigate the α-In2Se3 in different thicknesses and report that the THz generation efficiency induced by femtosecond laser pulses can be largely improved by reducing the thickness from the bulk. Furthermore, we reveal the surge current in thin film coupled with THz emission exhibits a different Auger recombination mode, which is helpful in understanding the mechanism and provides insights into the design of 2D highly efficient THz devices.

Two-dimensional transition metal dichalcogenides (TMDs) have intriguing physic properties and offer an exciting platform to explore many features that are important for future devices. In this work, we synthesized monolayer WS₂ as an example to study the optical response with hydrostatic pressure. The Raman results show a continuous tuning of the lattice vibrations that is induced by hydrostatic pressure. We further demonstrate an efficient pressure-induced change of the band structure and carrier dynamics via transient absorption measurements. We found that two time constants can be attributed to the capture process of two kinds of defect states, with the pressure increasing from 0.55 GPa to 2.91 GPa, both of capture processes were accelerated, and there is an inflection point within the pressure range of 1.56 GPa to 1.89 GPa. Our findings provide valuable information for the design of future optoelectronic devices.

二维材料及其异质结构由于其独特的结构和优异的光电性能，有望成为下一代光电子技术的核心材料。光生载流子的动力学性质对这些材料的光电性能具有重要的影响。本文综述了近年来对这些材料中光生载流子动力学过程的研究进展。在时域动力学方面，介绍了利用基于超快激光的瞬态吸收光谱技术所揭示的二维材料中的载流子热化、能量弛豫、激子形成、激子?激子湮灭、以及激子复合等物理过程。在空域动力学方面，讨论了利用具有高空间分辨率的瞬态吸收显微技术来研究光生载流子在二维材料平面内的输运过程。在此基础上，进一步讨论了二维材料异质结构中的电荷及能量在层间转移的过程。

基于自建的超快抽运探测实验系统，研究了化学气相沉积法生长的SnSe₂薄膜的超快载流子与声子动力学。对SnSe₂薄膜随抽运能量密度变化的载流子弛豫过程的测量结果表明该薄膜具有超快的载流子热化过程和皮秒至纳秒时间尺度的复合过程。伴随着光生载流子的超快激发和能量弛豫，SnSe₂薄膜发生晶格热化，产生了特定频率的相干声学声子。通过分析声学声子振荡信号随抽运能量密度变化的规律，揭示了SnSe₂薄膜产生的相干声学声子的特性。研究结果对SnSe₂薄膜在光电器件领域的应用研究具有一定的参考价值。

Despite that organic-inorganic lead halide perovskites have attracted enormous scientific attention for energy conversion applications over the recent years, the influence of temperature and the type of the employed hole transport layer (HTL) on the charge carrier dynamics and recombination processes in perovskite photovoltaic devices is still largely unexplored. In particular, significant knowledge is missing on how these crucial parameters for radiative and non-radiative recombinations, as well as for efficient charge extraction vary among different perovskite crystalline phases that are induced by temperature variation. Herein, we perform micro photoluminescence (μPL) and ultrafast time resolved transient absorption spectroscopy (TAS) in Glass/Perovskite and two different Glass/ITO/HTL/Perovskite configurations at temperatures below room temperature, in order to probe the charge carrier dynamics of different perovskite crystalline phases, while considering also the effect of the employed HTL polymer. Namely, CH₃NH₃PbI₃ films were deposited on Glass, PEDOT:PSS and PTAA polymers, and the developed Glass/CH₃NH₃PbI₃ and Glass/ITO/HTL/CH₃NH₃PbI₃ architectures were studied from 85 K up to 215 K in order to explore the charge extraction dynamics of the CH₃NH₃PbI₃ orthorhombic and tetragonal crystalline phases. It is observed an unusual blueshift of the bandgap with temperature and the dual emission at temperature below of 100 K and also, that the charge carrier dynamics, as expressed by hole injection times and free carrier recombination rates, are strongly depended on the actual pervoskite crystal phase, as well as, from the selected hole transport material.Despite that organic-inorganic lead halide perovskites have attracted enormous scientific attention for energy conversion applications over the recent years, the influence of temperature and the type of the employed hole transport layer (HTL) on the charge carrier dynamics and recombination processes in perovskite photovoltaic devices is still largely unexplored. In particular, significant knowledge is missing on how these crucial parameters for radiative and non-radiative recombinations, as well as for efficient charge extraction vary among different perovskite crystalline phases that are induced by temperature variation. Herein, we perform micro photoluminescence (μPL) and ultrafast time resolved transient absorption spectroscopy (TAS) in Glass/Perovskite and two different Glass/ITO/HTL/Perovskite configurations at temperatures below room temperature, in order to probe the charge carrier dynamics of different perovskite crystalline phases, while considering also the effect of the employed HTL polymer. Namely, CH₃NH₃PbI₃ films were deposited on Glass, PEDOT:PSS and PTAA polymers, and the developed Glass/CH₃NH₃PbI₃ and Glass/ITO/HTL/CH₃NH₃PbI₃ architectures were studied from 85 K up to 215 K in order to explore the charge extraction dynamics of the CH₃NH₃PbI₃ orthorhombic and tetragonal crystalline phases. It is observed an unusual blueshift of the bandgap with temperature and the dual emission at temperature below of 100 K and also, that the charge carrier dynamics, as expressed by hole injection times and free carrier recombination rates, are strongly depended on the actual pervoskite crystal phase, as well as, from the selected hole transport material.

基于超快时间分辨光谱实验手段，研究了化学气相沉积（chemical vapor deposition，CVD）生长的ReS₂薄膜的超快载流子动力学和太赫兹发射。分别利用光泵浦探测和光泵浦太赫兹发射两套系统对ReS₂薄膜进行了测试，结果表明：ReS₂薄膜具有超快的载流子热化过程和亚纳秒量级的复合过程；在飞秒激光泵浦下能够产生频谱宽度为2.5 THz的太赫兹辐射。通过分析太赫兹辐射随泵浦光入射角改变而出现极性相反的现象，得出ReS₂薄膜产生太赫兹辐射的主要机制为表面场效应。研究结果不仅有助于理解ReS₂薄膜对超快激光脉冲的瞬态响应，而且为太赫兹光子器件（如太赫兹发射器等）的研究设计提供了重要参考。

新型光电材料、磁性材料、低维量子材料等是目前凝聚态物理的研究前沿，其在微纳尺度的近场光学动力学具有丰富的物理内涵和广阔的应用前景。飞秒激光的超高时间分辨与光电子显微镜的超高空间分辨结合为一种超高时空分辨测量技术，为材料物理、表面物理等研究注入了新的活力，提供了强有力的平台。本文介绍了超高时空分辨光电子显微镜，讨论了其在金属表面等离激元动力学、低维材料等新型半导体材料动力学、材料异质结界面动力学等方面的应用和研究进展，最后展望了其在飞秒-纳米尺度表面和界面物理研究的应用前景。

原子级厚度的单层或者少层二维过渡金属硫族化合物因其独特的物理特性而被寄希望成为下一代光电子器件的重要组成部分。然而，二维材料的缺陷在很大程度上影响着材料的性质。一方面，缺陷的存在降低了材料的荧光量子效率、载流子迁移率等重要参数，影响了器件的性能。另一方面，合理地调控和利用缺陷催生了单光子源等新的应用，因此，表征、理解、处理和调控二维材料中的缺陷至关重要。本文综述了二维过渡金属硫族化合物中的缺陷以及缺陷相关的载流子动力学研究进展，旨在梳理二维材料中的缺陷及其超快动力学与材料性能之间的关系，为二维过渡金属硫族化合物材料特性和高性能光电子器件的相关研究提供支持。