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Thermoelectrics (TEs) have been considered a sustainable and eco-friendly energy technology. However, due to limitations in energy conversion efficiency, TE devices have not yet been widely adopted. Here, we proposed a class of TE materials, trigonal XPt2Se3 (X = K, Rb), with the same crystal structure as Bi2Te3. At room temperature, with quartic anharmonicity correction, the lattice thermal conductivity (κL) of KPt2Se3 and RbPt2Se3 in the x-direction is only 0.57 and 0.46 W m−1 K−1, respectively. The ultralow κL arises from their layered structure, strong lattice anharmonicity, weak bonding nature, rattling motion of guest alkali metal atoms, and large scattering space. Simultaneously, the large density of states contributes to large power factors. At 800 K, both under n-type and p-type doping, KPt2Se3 exhibits ZT values that can exceed 4 in specific directions, while RbPt2Se3's ZT values can surpass 3, which is significantly higher than traditional TE materials. Our research not only elucidates that the layered trigonal crystals XPt2Se3 (X = K, Rb) represent a category of potential TE materials with ultralow κL and high TE performance but also provides directions for exploring TE materials. [ABSTRACT FROM AUTHOR]

All-inorganic perovskite quantum dots (PeQDs) have aroused great research interest in white light-emitting diodes (WLED) due to their excellent optoelectronic properties, but the poor stability, caused by dynamically binding long-chain capping ligands, hinders their future practical applications. To address this issue, here, we exploit short-chain butyric acid (BA) to replace long-chain oleic acid (OA) as capping ligand of CsPbX3 PeQDs by a hot-injection method. The addition of BA not only makes the morphology of CsPbBr3 PeQDs uniform and improves the crystallinity but also effectively suppresses nonradiative recombination, achieving a near unit photoluminescence quantum yield of 96%. The BA capped CsPbBr3 PeQDs exhibit high stability up to 180 d stored in ambient environment and also significantly improved resistance against polar solvent, ultra-violet lamp irradiation, and heat, which is rationalized by the strong binding capacity and shortened distance of BA to the PeQDs through ab initio calculations. Furthermore, by combining green-emission CsPbBr3 and red-emission CsPbBr0.8I2.2 PeQDs with blue GaN chip, we achieved WLEDs with excellent luminous properties, showing their great potential in practical application of wide-color-gamut display and lighting. [ABSTRACT FROM AUTHOR]

MoSH is a representative example of a Janus two-dimensional monolayered system consisting of a molybdenum atomic layer sandwiched between sulfur and hydrogen atomic layers. Extensive experimental and theoretical efforts have suggested the great promise of the MoSH material, but the validity of the MoSH model (with a Mo–S–H ratio of 1:1:1) remains uncertain. While various experiments have established the Mo-to-S ratio to be close to 1:1, the hydrogen content has remained elusive even with the use of state-of-the-art characterization techniques due to its lightweight nature. In this study, we present a theoretical investigation aiming to determine the positions and ratios of the hydrogen atoms on MoSHx (with x ranging from 0 to 3) as well as assess their structural stability. By evaluating the energetic, mechanical, and thermodynamic properties, we confirm the existence of stable MoSHx structures within a critical range of hydrogen atom ratios, specifically 0.5 ≤ x ≤ 2.0. Additionally, as the hydrogen atom ratio increases, we observe a transition in the preferred adsorption sites of hydrogen atoms from the center of the hexagonal ring composed of molybdenum and sulfur atoms to the upper region of the molybdenum atoms. This study offers critical insight into the structural characteristics and stability of Janus monolayer MoSHx, contributing to the advancement and application of Janus MoSHx in various fields. [ABSTRACT FROM AUTHOR]

Structural phase transition materials have attracted extensive attention in various fields due to their tunable physical properties. Transition metal dichalcogenide (TMD) nanomaterial is a critical representation. However, the phase transition of Janus MoSH, a sub-member of TMD nanomaterial, remains poorly understood. In this study, we employed a theoretical approach to investigate the phase transition of MoSH monolayer. Our results reveal temperature-dependent structural phase transitions of MoSH from 2H to 1T′. As the temperature reaches a critical value, a spontaneous structural phase transition occurs from 2H to 1T′ phase. Remarkably, our study identifies the 1T′ phase of MoSH as the most stable phase (including energetic, mechanical, dynamic, and thermodynamic stability) at most temperature ranges, and we provide insight into the reaction pathway of MoSH from 2H to 1T′ phase. Moreover, the structural phase transition of MoSH with hydrogen vacancies is also temperature-dependent, with the critical temperature decreasing with the incremental number of vacancies. Overall, our findings not only reveal the temperature-dependent structural phase transition of MoSH but also confirm the stable structure of MoSH in 1T′ phase at room temperature, which is significant for potential applications of 2D MoSH nanomaterial. [ABSTRACT FROM AUTHOR]