间接带隙的Cs₂NaBiCl₆双钙钛矿材料具有近红外宽波段发射特性, 但低发光效率限制了其在近红外发光领域的应用。本工作通过共沉淀法快速制备微米级尺寸的Cs₂Ag_0.1Na_0.9BiCl₆:Tm³⁺双钙钛矿晶体, 实现了近红外荧光增强, 并系统研究了其光学吸收、光致发射(PL)、光致激发(PLE)、时间分辨光致发光和荧光量子效率(PLQY)等光学性能。共沉淀法制备的Cs₂Ag_0.1Na_0.9BiCl₆:Tm³⁺的光学带隙为3.06 eV。在350 nm紫外光激发下, 可以观察到峰值位于680 nm的近红外宽峰发射, 这源于自陷激子发光。通过引入Tm³⁺作为新的发光中心, 实现了810 nm波段的近红外发光增强, 在780~830 nm波段荧光量子效率(PLQY)从1.67%提高到11.77%, 提高了6.05倍。在650~900 nm波段, Cs₂Ag_0.1Na_0.9BiCl₆:Tm³⁺的近红外PLQY高达25.22%。本研究证明了共沉淀法快速制备的Cs₂Ag_0.1Na_0.9BiCl₆:Tm³⁺钙钛矿作为新型近红外光源材料的可行性。

由于量子限制效应，自组装半导体单量子点具有类似于原子的分立能级，可实现高不可分辨、高亮度和高纯度的单光子发射，其多种激子态能够产生不同偏振模式的光子。而光学微纳结构是调控量子点发光性质的有效手段，当单个量子点与光学微腔发生弱耦合时，Purcell效应将大大提高量子点作为单光子源或纠缠光子对源的性能。同时，量子点与光学微腔的强耦合系统可以作为量子光学网络中的量子节点，以及用于研究单光子水平的光学非线性效应。利用量子点与光学波导的耦合可实现固态量子比特和飞行光子比特的相干转换，以及高效的信息处理与传输，由此构建可靠的片上光学网络。此外，单量子点还具有可操控的自旋态，可作为量子比特的载体。考虑到量子点器件的制备过程易与成熟的半导体技术相结合，基于量子点的器件设计具有良好的可扩展性和集成化潜力。

Monolayer group VI transition metal dichalcogenides (TMDs) have recently emerged as promising candidates for photonic and opto-valleytronic applications. The optoelectronic properties of these atomically-thin semiconducting crystals are strongly governed by the tightly bound electron-hole pairs such as excitons and trions (charged excitons). The anomalous spin and valley configurations at the conduction band edges in monolayer WS₂ give rise to even more fascinating valley many-body complexes. Here we find that the indirect Q valley in the first Brillouin zone of monolayer WS₂plays a critical role in the formation of a new excitonic state, which has not been well studied. By employing a high-quality h-BN encapsulated WS₂ field-effect transistor, we are able to switch the electron concentration within K-Q valleys at conduction band edges. Consequently, a distinct emission feature could be excited at the high electron doping region. Such feature has a competing population with the K valley trion, and experiences nonlinear power-law response and lifetime dynamics under doping. Our findings open up a new avenue for the study of valley many-body physics and quantum optics in semiconducting 2D materials, as well as provide a promising way of valley manipulation for next-generation entangled photonic devices.

Moiré materials, composed of two single-layer two-dimensional semiconductors, are important because they are good platforms for studying strongly correlated physics. Among them, moiré materials based on transition metal dichalcogenides (TMDs) have been intensively studied. The hetero-bilayer can support moiré interlayer excitons if there is a small twist angle or small lattice constant difference between the TMDs in the hetero-bilayer and form a type-II band alignment. The coupling of moiré interlayer excitons to cavity modes can induce exotic phenomena. Here, we review recent advances in the coupling of moiré interlayer excitons to cavities, and comment on the current difficulties and possible future research directions in this field.Moiré materials, composed of two single-layer two-dimensional semiconductors, are important because they are good platforms for studying strongly correlated physics. Among them, moiré materials based on transition metal dichalcogenides (TMDs) have been intensively studied. The hetero-bilayer can support moiré interlayer excitons if there is a small twist angle or small lattice constant difference between the TMDs in the hetero-bilayer and form a type-II band alignment. The coupling of moiré interlayer excitons to cavity modes can induce exotic phenomena. Here, we review recent advances in the coupling of moiré interlayer excitons to cavities, and comment on the current difficulties and possible future research directions in this field.

Moiré superlattices are formed when overlaying two materials with a slight mismatch in twist angle or lattice constant. They provide a novel platform for the study of strong electronic correlations and non-trivial band topology, where emergent phenomena such as correlated insulating states, unconventional superconductivity, and quantum anomalous Hall effect are discovered. In this review, we focus on the semiconducting transition metal dichalcogenides (TMDs) based moiré systems that host intriguing flat-band physics. We first review the exfoliation methods of two-dimensional materials and the fabrication technique of their moiré structures. Secondly, we overview the progress of the optically excited moiré excitons, which render the main discovery in the early experiments on TMD moiré systems. We then introduce the formation mechanism of flat bands and their potential in the quantum simulation of the Hubbard model with tunable doping, degeneracies, and correlation strength. Finally, we briefly discuss the challenges and future perspectives of this field.Moiré superlattices are formed when overlaying two materials with a slight mismatch in twist angle or lattice constant. They provide a novel platform for the study of strong electronic correlations and non-trivial band topology, where emergent phenomena such as correlated insulating states, unconventional superconductivity, and quantum anomalous Hall effect are discovered. In this review, we focus on the semiconducting transition metal dichalcogenides (TMDs) based moiré systems that host intriguing flat-band physics. We first review the exfoliation methods of two-dimensional materials and the fabrication technique of their moiré structures. Secondly, we overview the progress of the optically excited moiré excitons, which render the main discovery in the early experiments on TMD moiré systems. We then introduce the formation mechanism of flat bands and their potential in the quantum simulation of the Hubbard model with tunable doping, degeneracies, and correlation strength. Finally, we briefly discuss the challenges and future perspectives of this field.

Two-dimensional (2D) semiconductors have captured broad interest as light emitters, due to their unique excitonic effects. These layer-blocks can be integrated through van der Waals assembly,i.e., fabricating homo- or heterojunctions, which show novel emission properties caused by interface engineering. In this review, we will first give an overview of the basic strategies that have been employed in interface engineering, including changing components, adjusting interlayer gap, and tuning twist angle. By modifying the interfacial factors, novel emission properties of emerging excitons are unveiled and discussed. Generally, well-tailored interfacial energy transfer and charge transfer within a 2D heterostructure cause static modulation of the brightness of intralayer excitons. As a special case, dynamically correlated dual-color emission in weakly-coupled bilayers will be introduced, which originates from intermittent interlayer charge transfer. For homobilayers and type Ⅱ heterobilayers, interlayer excitons with electrons and holes residing in neighboring layers are another important topic in this review. Moreover, the overlap of two crystal lattices forms moiré patterns with a relatively large period, taking effect on intralayer and interlayer excitons. Particularly, theoretical and experimental progresses on spatially modulated moiré excitons with ultra-sharp linewidth and quantum emission properties will be highlighted. Moiré quantum emitter provides uniform and integratable arrays of single photon emitters that are previously inaccessible, which is essential in quantum many-body simulation and quantum information processing. Benefiting from the optically addressable spin and valley indices, 2D heterostructures have become an indispensable platform for investigating exciton physics, designing and integrating novel concept emitters.Two-dimensional (2D) semiconductors have captured broad interest as light emitters, due to their unique excitonic effects. These layer-blocks can be integrated through van der Waals assembly,i.e., fabricating homo- or heterojunctions, which show novel emission properties caused by interface engineering. In this review, we will first give an overview of the basic strategies that have been employed in interface engineering, including changing components, adjusting interlayer gap, and tuning twist angle. By modifying the interfacial factors, novel emission properties of emerging excitons are unveiled and discussed. Generally, well-tailored interfacial energy transfer and charge transfer within a 2D heterostructure cause static modulation of the brightness of intralayer excitons. As a special case, dynamically correlated dual-color emission in weakly-coupled bilayers will be introduced, which originates from intermittent interlayer charge transfer. For homobilayers and type Ⅱ heterobilayers, interlayer excitons with electrons and holes residing in neighboring layers are another important topic in this review. Moreover, the overlap of two crystal lattices forms moiré patterns with a relatively large period, taking effect on intralayer and interlayer excitons. Particularly, theoretical and experimental progresses on spatially modulated moiré excitons with ultra-sharp linewidth and quantum emission properties will be highlighted. Moiré quantum emitter provides uniform and integratable arrays of single photon emitters that are previously inaccessible, which is essential in quantum many-body simulation and quantum information processing. Benefiting from the optically addressable spin and valley indices, 2D heterostructures have become an indispensable platform for investigating exciton physics, designing and integrating novel concept emitters.

有机发光二极管（OLEDs）是基于有机半导体的发光器件，由于具有自发光、响应速度快、发光颜色可调、轻薄、大面积柔性可弯曲等优点，被认为是新一代的显示和照明技术。OLEDs是通过注入的电子和空穴复合形成激子并辐射发光的过程，因此如何有效利用激子，特别是三线态激子，已经成为OLEDs材料和器件研究的重要课题。其中，如何把三线态激子能量转换成单线态激子，并最终实现100%激子的荧光发射更具有应用价值，最近几年这方面的研究已经取得了显著进展。本文从OLEDs的工作原理和发光过程出发，详细介绍了制备高效率荧光OLEDs的有效方法及其最新进展，并对未来发展方向进行了展望，为OLEDs材料和器件的研究提供重要参考。