Guidelines for the characterization of metal halide nanocrystals

Partial Ligand Stripping from CsPbBr3 Nanocrystals Improves Their Performance in Light-Emitting Diodes

Halide perovskite nanocrystals (NCs), specifically CsPbBr3, have attracted considerable interest due to their remarkable optical properties for optoelectronic devices. To achieve high-efficiency light-emitting diodes (LEDs) based on CsPbBr3 nanocrystals (NCs), it is crucial to optimize both their photoluminescence quantum yield (PLQY) and carrier transport properties when they are deposited to form films on substrates. While the exchange of native ligands with didodecyl dimethylammonium bromide (DDAB) ligand pairs has been successful in boosting their PLQY, dense DDAB coverage on the surface of NCs should impede carrier transport and limit device efficiency. Following our previous work, here, we use oleyl phosphonic acid (OLPA) as a selective stripping agent to remove a fraction of DDAB from the NC surface and demonstrate that such stripping enhances carrier transport while maintaining a high PLQY. Through systematic optimization of OLPA dosage, we significantly improve the performance of CsPbBr3 LEDs, achieving a maximum external quantum efficiency (EQE) of 15.1% at 516 nm and a maximum brightness of 5931 cd m-2. These findings underscore the potential of controlled ligand stripping to enhance the performance of CsPbBr3 NC-based optoelectronic devices.

Design Rules for Obtaining Narrow Luminescence from Semiconductors Made in Solution

Solution-processed semiconductors are in demand for present and next-generation optoelectronic technologies ranging from displays to quantum light sources because of their scalability and ease of integration into devices with diverse form factors. One of the central requirements for semiconductors used in these applications is a narrow photoluminescence (PL) line width. Narrow emission line widths are needed to ensure both color and single-photon purity, raising the question of what design rules are needed to obtain narrow emission from semiconductors made in solution. In this review, we first examine the requirements for colloidal emitters for a variety of applications including light-emitting diodes, photodetectors, lasers, and quantum information science. Next, we will delve into the sources of spectral broadening, including "homogeneous" broadening from dynamical broadening mechanisms in single-particle spectra, heterogeneous broadening from static structural differences in ensemble spectra, and spectral diffusion. Then, we compare the current state of the art in terms of emission line width for a variety of colloidal materials including II-VI quantum dots (QDs) and nanoplatelets, III-V QDs, alloyed QDs, metal-halide perovskites including nanocrystals and 2D structures, doped nanocrystals, and, finally, as a point of comparison, organic molecules. We end with some conclusions and connections, including an outline of promising paths forward.

Recent Developments of Microscopic Study for Lanthanide and Manganese Doped Luminescent Materials

Luminescent materials are indispensable for applications in lighting, displays and photovoltaics, which can transfer, absorb, store and utilize light energy. Their performance is closely related with their size and morphologies, exact atomic arrangement, and local configuration about photofunctional centers. Advanced electron microscopy-based techniques have enabled the possibility to study nanostructures with atomic resolution. Especially, with the advanced micro-electro-mechanical systems, it is able to characterize the luminescent materials at the atomic scale under various environments, providing a deep understanding of the luminescent mechanism. Accordingly, this review summarizes the recent achievements of microscopic study to directly image the microstructure and local environment of activators in lanthanide and manganese (Ln/Mn²⁺ )-doped luminescent materials, including: 1) bulk materials, the typical systems are nitride/oxynitride phosphors; and 2) nanomaterials, such as nanocrystals (hexagonal-phase NaLnF₄ and perovskite) and 2D nanosheets (Ca₂ Ta₃ O₁₀ and MoS₂ ). Finally, the challenges and limitations are highlighted, and some possible solutions to facilitate the developments of advanced luminescent materials are provided.

Dealloying Synthesis of Silicon Nanotubes for High-performance Lithium Ion Batteries

Practical applications of silicon based anodes in lithium ion batteries have attracted unprecedented attentions due to the merits of extraordinary energy density, high safety and low cost. Nevertheless, the inevitable huge volume change upon lithiation and delithiation brings about silicon electrode integrity damage and fast capacity fading, hampering the large-scale application. Herein, a novel one-dimensional tubular silicon-nitrogen doped carbon composite (Si@NC) with a core-shell structure has been fabricated using silicon magnesium alloy and polydopamine as a template and precursor. The as-obtained composite exhibits remarkable specific capacity and ultrafast redox kinetics, an outstanding cycling stability with fine capacity of 583.6 mAh g-1 at 0.5 A g-1 over 200 cycles is delivered. Moreover, a full cell matched with LiFePO4 cathode has demonstrated a reversible capacity of 148.8 mAh g-1 with high Coulombic efficiency as well as an excellent energy density of 396 Wh kg-1. The nanotube structure engineering and silicon confined in nitrogen doped carbon effectively alleviate the volume expansion and endow the composite with superior stability. The robust strategy developed here gives a new insight into designing silicon anodes for enhanced lithium storage properties.