Enhancing crystal integrity and structural rigidity of CsPbBr nanoplatelets to achieve a narrow color-saturated blue emission.

Quantum-confined CsPbBr perovskites are promising blue emitters for ultra-high-definition displays, but their soft lattice caused by highly ionic nature has a limited stability. Here, we endow CsPbBr nanoplatelets (NPLs) with atomic crystal-like structural rigidity through proper surface engineering, by using strongly bound N-dodecylbenzene sulfonic acid (DBSA). A stable, rigid crystal structure, as well as uniform, orderly-arranged surface of these NPLs is achieved by optimizing intermediate reaction stage, by switching from molecular clusters to mono-octahedra, while interaction with DBSA resulted in formation of a CsO monolayer shell capping the NPL surface.

Entropy-Driven Strongly Confined Low-Toxicity Pure-Red Perovskite Quantum Dots for Spectrally Stable Light-Emitting Diodes.

Spectrally stable pure-red perovskite quantum dots (QDs) with low lead content are essential for high-definition displays but are difficult to synthesize due to QD self-purification. Here, we make use of entropy-driven quantum-confined pure-red perovskite QDs to fabricate light-emitting diodes (LEDs) that have low toxicity and are efficient and spectrum-stable. Based on experimental data and first-principles calculations, multiple element alloying results in a 60% reduction in lead content while improving QD entropy to promote crystal stability.

Overcoming the Ambient Manufacturability-Performance Bottleneck in Perovskite Nanocrystal Emitters for Efficient Light-Emitting Diodes.

Colloidal perovskite nanocrystals (NCs) have risen rapidly in luminescence efficiency and color purity. However, their high performance requires careful and complex pre-treatment of precursors and precise regulation of the reaction atmosphere; otherwise, their emission will be weak and broad. To overcome these limitations, we develop a facile ligand exchange method using a new type of bidentate ligand, which is obtained by reacting cheap sulfur with tributylphosphine (S-TBP).

Amine-Terminated Carbon Dots Linking Hole Transport Layer and Vertically Oriented Quasi-2D Perovskites through Hydrogen Bonds Enable Efficient LEDs.

Close attention to the interfaces of solution-processed metal halide perovskite-based light-emitting devices (LEDs) is crucial for their optimal performance. Solution processing of these devices typically leads to the formation of van der Waals interfaces with a weak connection between different functional layers, leaving great room for improvement in charge transport through strengthening of the interlayer interaction. Here, we have realized a hydrogen-bond-assisted interface that makes use of ultrasmall amine-terminated carbon dots to enhance the interaction between the hole transport layer made of PEDOT:PSS and the hybrid lead bromide perovskite emitting layer, which not only promotes the hole injection efficiency but also orients the quasi-2D perovskite crystals penetrating the vertical direction of the device without any, or very few, horizontal grain boundaries, which has a profound effect on the photophysical and transport properties of the emitting layer.

Improved One- and Multiple-Photon Excited Photoluminescence from Cd-Doped CsPbBr Perovskite NCs.

Metal halide perovskite nanocrystals (NCs) attract much attention for light-emitting applications due to their exceptional optical properties. More recently, perovskite NCs have begun to be considered a promising material for nonlinear optical applications. Numerous strategies have recently been developed to improve the properties of metal halide perovskite NCs.

Methanol-induced fast CsBr release results in phase-pure CsPbBr perovskite nanoplatelets.

Formation of a non-emissive wide bandgap CsPbBr component often accompanies the synthesis of CsPbBr perovskites, introducing undesired energy states and impeding the charge transport. Here, we demonstrate that a small amount of a methanol additive can promote the CsBr release rate, facilitating CsPbBr formation and suppressing CsPbBr formation. Some of the methanol ionizes into CHO and CHO, which act as surface ligands and change the crystallization environment, inducing shape evolution from spherical nanocrystals to rectangular nanoplatelets (NPLs), leading to monodispersed and phase-pure 8 unit-cell-thick CsPbBr NPLs.

Ruddlesden-Popper Perovskites: Synthesis and Optical Properties for Optoelectronic Applications.

Ruddlesden-Popper perovskites with a formula of (A')(A) B X have recently gained widespread interest as candidates for the next generation of optoelectronic devices. The variations of organic cation, metal halide, and the number of layers in the structure lead to the change of crystal structures and properties for different optoelectronic applications. Herein, the different synthetic methods for 2D perovskite crystals and thin films are summarized and compared.

Yb and Yb/Er Doping for Near-Infrared Emission and Improved Stability of CsPbCl Nanocrystals.

Lead halide perovskite nanocrystals (NCs) exhibit excellent tunable emissions covering the entire visible spectral region, but they do not emit near-infrared (NIR) light. We synthesized rare earth element doped CsPbCl NCs for NIR emission. The Yb doped CsPbCl NCs emitted strong 986 nm NIR light; the Yb/Er co-doped CsPbCl NCs emitted at 1533 nm.

Low-temperature one-pot synthesis of WS nanoflakes as electrocatalyst for hydrogen evolution reaction.

Transition metal dichalcogenides have unique physicochemical properties. Herein, a low-temperature facile method is demonstrated to synthesize ultrathin tungsten disulfide nanoflakes. They are loosely stacked between layers with highly exposed edges, which provide lots of active sites for electrochemical applications.

Rational Control of Size and Photoluminescence of WS Quantum Dots for White Light-Emitting Diodes.

Transition-metal dichalcogenides like tungsten disulfide (WS) are luminescent but still bear low quantum yields and hardly meet the requirement of practical applications. Here, we developed a hot-injection method to prepare highly luminescent WS quantum dots with tunable particle size in a noncoordinating solvent, some that are even smaller than its Bohr radius. The as-synthesized WS quantum dots exhibit a narrow size distribution and a high photoluminescence quantum yield of 32%, the highest record compared to the known reports.