Manipulating hyperbolic transient plasmons in a layered semiconductor.

Anisotropic materials with oppositely signed dielectric tensors support hyperbolic polaritons, displaying enhanced electromagnetic localization and directional energy flow. However, the most reported hyperbolic phonon polaritons are difficult to apply for active electro-optical modulations and optoelectronic devices. Here, we report a dynamic topological plasmonic dispersion transition in black phosphorus via photo-induced carrier injection, i.e., transforming the iso-frequency contour from a pristine ellipsoid to a non-equilibrium hyperboloid. Our work also demonstrates the peculiar transient plasmonic properties of the studied layered semiconductor, such as the ultrafast transition, low propagation losses, efficient optical emission from the black phosphorus's edges, and the characterization of different transient plasmon modes. Our results may be relevant for the development of future optoelectronic applications.

Laser doping of 2D material for precise energy band design.

The number of excellent 2D materials is finite for nano optoelectric devices including transistors, diodes, sensors, and so forth, thus the modulation of 2D materials is important to improve the performance of the current eligible 2D materials, and even to transform unqualified 2D materials into eligible 2D materials. Here we develop a fine laser doping strategy based on highly controllable laser direct writing, and investigate its effectivity and practicability by doping multilayer molybdenum ditelluride (MoTe2). Power-gradient laser doping and patterned laser doping, for the first time, are presented for designable and fine doping of 2D materials. The laser-induced polar transition of MoTe2 indicates good controllability of the method for the carrier concentration distribution in MoTe2. Multiple devices with finely tuned energy band structures are demonstrated by means of power-gradient laser doping and patterned laser doping, further illustrating the design capability of a precise energy band in 2D materials.

Plasmon-Enhanced Blue-Light Emission of Stable Perovskite Quantum Dot Membranes.

A series of stable and color-tunable MAPbBr3-xClx quantum dot membranes were fabricated via a cost-efficient high-throughput technology. MAPbBr3-xClx quantum dots grown in-situ in polyvinylidene fluoride electrospun nanofibers exhibit extraordinary stability. As polyvinylidene fluoride can prevent the molecular group MA+ from aggregating, MAPbBr3-xClx quantum dots are several nanometers and monodisperse in polyvinylidene fluoride fiber. As-prepared MAPbBr3-xClx quantum dot membranes exhibit the variable luminous color by controlling the Cl- content of MAPbBr3-xClx quantum dots. To improve blue-light emission efficiency, we successfully introduced Ag nanoparticle nanofibers into MAPbBr1.2Cl1.8 quantum dot membranes via layer-by-layer electrospinning and obtained ~4.8 folds fluorescence enhancement for one unit. Furthermore, the originality explanation for the fluorescence enhancement of MAPbBr3-xClx quantum dots is proposed based on simulating optical field distribution of the research system.