Investigation of Electrode Electrochemical Reactions in CH3 NH3 PbBr3 Perovskite Single-Crystal Field-Effect Transistors.

Optoelectronic devices based on metal halide perovskites, including solar cells and light-emitting diodes, have attracted tremendous research attention globally in the last decade. Due to their potential to achieve high carrier mobilities, organic-inorganic hybrid perovskite materials can enable high-performance, solution-processed field-effect transistors (FETs) for next-generation, low-cost, flexible electronic circuits and displays. However, the performance of perovskite FETs is hampered predominantly by device instabilities, whose origin remains poorly understood. Here, perovskite single-crystal FETs based on methylammonium lead bromide are studied and device instabilities due to electrochemical reactions at the interface between the perovskite and gold source-drain top contacts are investigated. Despite forming the contacts by a gentle, soft lamination method, evidence is found that even at such "ideal" interfaces, a defective, intermixed layer is formed at the interface upon biasing of the device. Using a bottom-contact, bottom-gate architecture, it is shown that it is possible to minimize such a reaction through a chemical modification of the electrodes, and this enables fabrication of perovskite single-crystal FETs with high mobility of up to ≈15 cm2 V-1 s-1 at 80 K. This work addresses one of the key challenges toward the realization of high-performance solution-processed perovskite FETs

Facile Preparation, Microstructure and Dielectric Properties of La(Cr_0.2Mn_0.2Fe_0.2Co_0.2Ni_0.2)O₃ Perovskite High-Entropy Ceramics

Preparation and properties of La(Cr0.2Mn0.2Fe0.2Co0.2Ni0.2)O3 high-entropy ceramics are investigated. La(Cr0.2Mn0.2Fe0.2Co0.2Ni0.2)O3 high-entropy ceramics are prepared by a traditional two-step solid-state reaction method in air. La(Cr0.2Mn0.2Fe0.2Co0.2Ni0.2)O3 single-phase powders are synthesized by calcining the mixed oxides at 1000 °C for 20 h. The high-entropy ceramics are sintered at 1350–1650 °C in a muffle furnace for 4 h by using the above powders. The phase compositions of the high-entropy ceramics at different temperatures are characterized by X-ray diffraction (XRD) with Cu Kα radiation. A field-emission scanning electron microscope with energy-dispersive spectroscopy (EDS) is used to observe the microstructures and analyze the elemental distributions. The hardness and dielectric properties are measured and discussed

A new environmental protection law, many old problems?: challenges to environmental governance in China

Through a three-year revision involving various stakeholders, China has enacted a new Environmental Protection Law (EPL). The new law seeks to harmonize economic and social development with environmental protection and for the first time establishes clear requirements for the construction of an ecological civilization. It toughens the penalties for environmental offences with specific articles and provisions for raising public awareness. It also places greater responsibility on local government and law enforcement for the protection of China’s environment. However, many of the problems identified in the old EPL and especially the obstacles to its implementation have not been fully addressed and resolved. Effective environmental governance entails not only environmental laws but also implementation mechanisms, accountability regimes, and institutional arrangements. Raising the status of the EPL and of the general environmental protection apparatus is only the first step to meeting China’s environmental challenges. More efforts in the area of enforcement and implementation will lead China to a cleaner future

Effect of Current Density on the Microstructure and Mechanical Properties of 3YSZ/Al2O3 Composites by Flash Sintering

The 3YSZ/40 wt% Al2O3 composites were prepared by flash sintering at a low furnace temperature (700 °C). The effects of the current density on the relative density and Vickers hardness of the composites were systematically investigated. The results showed that the relative densities and Vickers hardness of the samples increased gradually with the increasing of the current densities, and the relative density was as high as 94.2%. The Vickers hardness of 11.3 GPa was obtained under a current density of 102 mA/mm2. Joule heating and defects generation are suggested to be the main causes of rapid densification in flash sintering. The microstructure of the molten zone showed the formation of eutectic structures in the composite, suggesting that grain boundary overheating may have contributed to the formation of the molten zone

Anisotropic Piezoelectric Properties of Porous (Ba_0.85Ca_0.15)(Zr_0.1Ti_0.9)O₃ Ceramics with Oriented Pores through TBA-Based Freeze-Casting Method

Porous (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 (BCZT) piezoelectric ceramics with an oriented directional hole structure were prepared by using the tertbutyl alcohol (TBA)-based freeze-casting method. The influences of sintering temperatures on the microstructure and piezoelectric properties of porous BCZT ceramics were investigated both perpendicular and parallel to the freezing direction. With the increase in sintering temperatures and the porosities decreased from 58% to 42%, the compressive strength increased from 14.0 MPa to 25.0 MPa. In addition, the d33 value of 407 pC/N for the sample sintered at 1400 °C was obtained parallel to the freezing direction, which was 1.40 times that of the other direction

Spin‐coating fabrication of high‐yield and uniform organic thin‐film transistors via a primer template growth

Publication status: PublishedAbstractSolution coating of organic semiconductors offers great potential for achieving low‐cost and high‐throughput manufacturing of large‐area and flexible electronics. However, the solution processability of semiconducting small molecules for fabricating uniform and reliable thin‐film devices poses challenges due to the low viscosities of small‐molecule solutions. Here, we report a universal approach employing a primer template (PT) to enhance the spreadability of small‐molecule solutions on silicon wafers, enabling the spin‐coating fabrication of uniform thin films composed of millimeter‐scale grains with complete large‐area coverage and well‐ordered molecular packing. Using PT, we fabricated organic thin‐film transistors (OTFTs) using solutions containing various small molecules such as rubrene and 2‐decyl‐7‐phenyl‐[1]benzothieno[3,2‐b][1]benzothiophene. The device yield of all fabricated OTFTs is consistently 100% while achieving a high average mobility of 1.62 cm2 V−1 s−1 with a device‐to‐device variation of 7.7% measured in ambient air condition. In addition, the utilization of PT resulted in a batch‐to‐batch variation of 12.5% in device performance over dozens of OTFT devices. The key industrial manufacturing metrics, such as device yield, reproducibility, and performance uniformity of the PT OTFTs, are among the best for devices fabricated using solution spin‐coating techniques.</jats:p