"Nature" and "Science" Week (9.4-9.10) Frontiers of Materials Science

1. Large-area perovskite film for solvent-free and vacuum-free methods for high efficiency solar modules

(A solvent- and vacuum-free route to large-area perovskite films for efficient solar modules)
The latest advances in organic-inorganic hybrid perovskites for optoelectronics have been reported to have a power conversion efficiency of up to 22% for perovskite solar cells. Improvements in stability also enable them to be tested over thousands of hours. However, such batteries require large-scale deployment of the ability to produce a large area of ​​uniform high quality perovskite film. A key challenge is to overcome the significant reduction in power conversion efficiency when small devices are amplified: when the common aperture area of ​​approximately 0.1 square centimeter increases to more than 25 square centimeters, conversion efficiency is found to decrease from 20% to approximately 10%. Chen et al. reported a novel deposition pathway for a methylammonium halide lead perovskite film that does not rely on common solvents or vacuums: instead, it relies on the rapid conversion of the amine complex precursor to a perovskite film, and then This is followed by a pressurization step. The thus deposited perovskite film has no pores and is highly uniform. More importantly, the new deposition method can be carried out in low temperature air, which is conducive to the manufacture of large-area perovskite devices. For the mesoporous TiO2-based perovskite solar module architecture, a power conversion efficiency of 12.1% was achieved with an open area of ​​36.1 square centimeters. (Nature DOI: 10.1038/nature23877)

2. Direct instrumental identification of catalytically active surface sites
Direct monitoring and determination of heterogeneously catalyzed active sites during the reaction facilitates the development of heterogeneous catalysis and electrocatalysts in practical applications. The inventions of scanning tunneling microscopy (STM) and electrochemical STM are promising for direct imaging, facilitating the understanding of heterogeneous catalysis at the atomic scale. Although STM has been applied to the detection and excitation of surface reactions and can make local reactivity measurements of certain systems possible, it is generally considered that STM is not suitable for directly determining catalytically active sites during the reaction. Pfisterer et al. demonstrated that conventional STM can easily achieve high-resolution imaging of catalytic surface activity: by detecting relative changes in tunneling current noise, it is possible to distinguish activity from near-quantitative forms based on the activity of hydrogen production or oxygen reduction reactions at these sites. Site. These data allow researchers to directly assess the importance and contribution of different defects or sites to overall catalytic activity. This method is expected to facilitate the rational design of heterogeneous catalysts. (Nature, DOI: 10.1038/nature23661)

3. Quantum simulations with ultracold atoms in optical lattices
As a branch of quantum computing, quantum simulation can provide valuable insights into difficult quantum problems in physics or chemistry. The ultracold atoms in the optical lattice represent an ideal platform for simulating quantum multibody problems. In this case, quantum gas microscopy can perform single atom observation and manipulation in large samples. Quantum magnets based on ultra-cold atoms have been used to detect quantum magnetism, to implement and detect topological quantum matter, and to study quantum systems with controlled remote interactions. Experiments with unbalanced multibody systems also provide results that are difficult to obtain with state-of-the-art supercomputers. Gross et al. reviewed recent experimental developments in this area and commented on future directions. (Science DOI: 10.1126/science.aal3837)

4. Probing the frontiers of particle physics with tabletop-scale experiments
The field of particle physics is in a special state. The standard model of particle theory successfully describes every elementary particle and force observed in the laboratory, but fails to explain the nature of the universe, such as the existence of dark matter, the amount of dark energy, and the superiority of matter on antimatter. The huge experiment of increasing scale and cost continues to look for new particles and forces that may explain these phenomena. However, these cutting-edge sciences have also been explored in some of the smaller, laboratory-scale "desktop" experiments. This method uses sophisticated measurement techniques and devices from atomic, quantum, and condensed matter physics to detect small signals due to new particles or forces. The discovery of basic physics is likely to come from this type of small-scale experiment. DeMille et al. reviewed the above. (Science DOI: 10.1126/science.aal3003)

5. Cold Molecules: Progress in Quantum Engineering in Chemistry and Quantum Physics (Cold molecules: Progress in quantum engineering of chemistry and quantum matter)
Cooling atoms to ultra-low temperatures has created numerous opportunities in basic physics, precision metrology, and quantum science. Due to the complexity of the molecular structure, the application of complex cooling techniques to molecules is more challenging, and now the door to precise control of the internal and external degrees of freedom of molecules and the long-term goals of the resulting interaction processes has been opened. This area of ​​research can use the basics to understand how molecules interact and evolve in order to be able to control reaction chemistry and design and implement a range of advanced quantum materials. Bohn et al. reviewed the above. (Science DOI: 10.1126/science.aam6299)

6. Efficient tomography of a quantum many-body system
Quantum tomography is a standard technique for estimating quantum states in small systems. However, as the required resources grow exponentially with increasing size, their application to larger systems quickly becomes impractical. Therefore, considerable efforts have been made to develop new characterization tools for quantum multibody states. Lanyon et al. demonstrated matrix-synchronous tomography, which theoretically proved to allow efficient and accurate estimation of a wide range of quantum states. Using this technique to reconstruct the dynamic state of a trapped ion quantum simulator can include up to 14 entangled and individually controlled spins: well beyond the practical limits of quantum tomography. The results of this study reveal the dynamic growth of entanglement and describe the relationship between its complexity and the diffusion of correlations during quenching: this is a necessary condition for future proofs beyond classical performance. Therefore, matrix product state tomography should be widely used in the research of a large number of sub-multibody systems and the benchmarking and verification of quantum simulators and computers. (Nature Physics DOI: 10.1038/NPHYS4244)

7. High dislocation density–induced large ductility in deformed and partitioned steels
High strength and high ductility materials are widely required in industrial applications. Unfortunately, strategies to increase material strength, such as manufacturing line defects (dislocations) during processing, tend to reduce the ductility of the material. He et al. developed a strategy to circumvent this problem in inexpensive medium manganese steel. Cold rolling followed by low temperature tempering treatment developed a steel with metastable austenite grains embedded in a highly dislocation martensite matrix. This deformation and delamination process (D&P) produces dislocation hardening, but maintains high ductility by enhancing the sliding of moving dislocations and allowing control of martensite transformation. The D&P strategy should also apply to any other alloy with deformation-induced martensite transformation, which provides a new way to develop high-strength, high-ductility materials. (Science DOI: 10.1126/science.aan0177)

8. Tetradymites as thermoelectrics and topological insulators
The stibnite is a M2X3 type compound crystallized in a rhombohedral structure, where M is a Group V metal, usually Bi or Sb, and X is an anion of Group VI such as Te, Se or S. Bi2Se3, Bi2Te3 and Sb2Te3 are typical stibnites. Other mixtures of M and X elements produce common variants such as Bi2Te2Se. Since stibnite is based on heavy p-block elements, strong spin-orbit coupling greatly affects its surface and bulk electron properties. The surface electronic state of stibnite is the cornerstone of the frontier work of topological insulators. The physical energy band is characterized by small energy gap, high group velocity and low effective mass, and can be inverted in the vicinity of the center of the Brillouin zone. These properties are advantageous for high efficiency thermoelectric materials, but also make it difficult to obtain electrical insulators, which is a requirement for topological insulators. Heremans et al. reviewed and reviewed recent advances in bulk and thin-walled stibnite materials in order to optimize the performance of stibnite materials as both thermoelectric and topological insulators. (Nature Reviews Materials DOI: 10.1038/natrevmats.2017.49)