The Synthesis of Three-Dimensional Hexagonal Boron Nitride as the Reinforcing Phase of Polymer-Based Electrolyte for All-Solid-State Li Metal Batteries.

Powdery hexagonal boron nitride (h-BN), as an important material for electrochemical energy storage, has been typically synthesized in bulk and one/two-dimensional (1/2D) nanostructured morphologies. However, until now, no method has been developed to synthesize powdery three-dimensional (3D) h-BN. This work introduces a novel NaCl-glucose-assisted strategy to synthesize micron-sized 3D h-BN with a honeycomb-like structure and its proposed formation mechanism.

Artificial Tactile Perceptual Neuron with Nociceptive and Pressure Decoding Abilities.

The neural system is a multifunctional perceptual learning system. Our brain can perceive different kinds of information to form senses, including touch, sight, hearing, and so on. Mimicking such perceptual learning systems is critical for neuromorphic platform applications.

Tunable Polaron Distortions Control the Extent of Halide Demixing in Lead Halide Perovskites.

Photoinduced phase separation in mixed halide perovskites emerges from their electro-mechanical properties and high ionic conductivities, resulting in photoinduced I-rich charge carrier traps that diminish photovoltaic performance. Whether photoinduced phase separation stems from the polycrystalline microstructure or is an intrinsic material property has been an open question. We investigate the nanoscale photoinduced behavior of single-crystal mixed Br/I methylammonium (MA) lead halide perovskite (MAPb(Br I)) nanoplates, eliminating effects from extended structural defects.

Strongly Quantum Confined Colloidal Cesium Tin Iodide Perovskite Nanoplates: Lessons for Reducing Defect Density and Improving Stability.

Within the last several years, metal halide perovskites such as methylammonium lead iodide, CHNHPbI, have come to the forefront of scientific investigation as defect-tolerant, solution-processable semiconductors that exhibit excellent optoelectronic properties. The vast majority of study has focused on Pb-based perovskites, which have limited applications because of their inherent toxicity. To enable the broad application of these materials, the properties of lead-free halide perovskites must be explored.

Ultralow thermal conductivity in all-inorganic halide perovskites.

Controlling the flow of thermal energy is crucial to numerous applications ranging from microelectronic devices to energy storage and energy conversion devices. Here, we report ultralow lattice thermal conductivities of solution-synthesized, single-crystalline all-inorganic halide perovskite nanowires composed of CsPbI (0.45 ± 0.

Atomic Resolution Imaging of Halide Perovskites.

The radiation-sensitive nature of halide perovskites has hindered structural studies at the atomic scale. We overcome this obstacle by applying low dose-rate in-line holography, which combines aberration-corrected high-resolution transmission electron microscopy with exit-wave reconstruction. This technique successfully yields the genuine atomic structure of ultrathin two-dimensional CsPbBr halide perovskites, and a quantitative structure determination was achieved atom column by atom column using the phase information of the reconstructed exit-wave function without causing electron beam-induced sample alterations.

Ultrathin Colloidal Cesium Lead Halide Perovskite Nanowires.

Highly uniform single crystal ultrathin CsPbBr nanowires (NWs) with diameter of 2.2 ± 0.2 nm and length up to several microns were successfully synthesized and purified using a catalyst-free colloidal synthesis method followed by a stepwise purification strategy.

Synthesis of Composition Tunable and Highly Luminescent Cesium Lead Halide Nanowires through Anion-Exchange Reactions.

Here, we demonstrate the successful synthesis of brightly emitting colloidal cesium lead halide (CsPbX3, X = Cl, Br, I) nanowires (NWs) with uniform diameters and tunable compositions. By using highly monodisperse CsPbBr3 NWs as templates, the NW composition can be independently controlled through anion-exchange reactions. CsPbX3 alloy NWs with a wide range of alloy compositions can be achieved with well-preserved morphology and crystal structure.

Lasing in robust cesium lead halide perovskite nanowires.

The rapidly growing field of nanoscale lasers can be advanced through the discovery of new, tunable light sources. The emission wavelength tunability demonstrated in perovskite materials is an attractive property for nanoscale lasers. Whereas organic-inorganic lead halide perovskite materials are known for their instability, cesium lead halides offer a robust alternative without sacrificing emission tunability or ease of synthesis.

Self-photosensitization of nonphotosynthetic bacteria for solar-to-chemical production.

Improving natural photosynthesis can enable the sustainable production of chemicals. However, neither purely artificial nor purely biological approaches seem poised to realize the potential of solar-to-chemical synthesis. We developed a hybrid approach, whereby we combined the highly efficient light harvesting of inorganic semiconductors with the high specificity, low cost, and self-replication and -repair of biocatalysts.

Atomically thin two-dimensional organic-inorganic hybrid perovskites.

Organic-inorganic hybrid perovskites, which have proved to be promising semiconductor materials for photovoltaic applications, have been made into atomically thin two-dimensional (2D) sheets. We report the solution-phase growth of single- and few-unit-cell-thick single-crystalline 2D hybrid perovskites of (C4H9NH3)2PbBr4 with well-defined square shape and large size. In contrast to other 2D materials, the hybrid perovskite sheets exhibit an unusual structural relaxation, and this structural change leads to a band gap shift as compared to the bulk crystal.

Growth and Anion Exchange Conversion of CH3NH3PbX3 Nanorod Arrays for Light-Emitting Diodes.

The nanowire and nanorod morphology offers great advantages for application in a range of optoelectronic devices, but these high-quality nanorod arrays are typically based on high temperature growth techniques. Here, we demonstrate the successful room temperature growth of a hybrid perovskite (CH3NH3PbBr3) nanorod array, and we also introduce a new low temperature anion exchange technique to convert the CH3NH3PbBr3 nanorod array into a CH3NH3PbI3 nanorod array while preserving morphology. We demonstrate the application of both these hybrid perovskite nanorod arrays for LEDs.

Core-Shell CdS-Cu₂S Nanorod Array Solar Cells.

As an earth-abundant p-type semiconductor, copper sulfide (Cu2S) is an attractive material for application in photovoltaic devices. However, it suffers from a minority carrier diffusion length that is less than the length required for complete light absorption. Core-shell nanowires and nanorods have the potential to alleviate this difficulty because they decouple the length scales of light absorption and charge collection.

Phase-selective cation-exchange chemistry in sulfide nanowire systems.

As a cation-deficient, p-type semiconductor, copper sulfide (Cu(2-x)S) shows promise for applications such as photovoltaics, memristors, and plasmonics. However, these applications demand precise tuning of the crystal phase as well as the stoichiometry of Cu(2-x)S, an ongoing challenge in the synthesis of Cu(2-x)S materials for a specific application. Here, a detailed transformation diagram of cation-exchange (CE) chemistry from cadmium sulfide (CdS) into Cu(2-x)S nanowires (NWs) is reported.

Three-dimensional spirals of atomic layered MoS2.

Atomically thin two-dimensional (2D) layered materials, including graphene, boron nitride, and transition metal dichalcogenides (TMDs), can exhibit novel phenomena distinct from their bulk counterparts and hold great promise for novel electronic and optoelectronic applications. Controlled growth of such 2D materials with different thickness, composition, and symmetry are of central importance to realize their potential. In particular, the ability to control the symmetry of TMD layers is highly desirable because breaking the inversion symmetry can lead to intriguing valley physics, nonlinear optical properties, and piezoelectric responses.