Efficient Perovskite Light-Emitting Diodes Using Polycrystalline Core-Shell-Mimicked Nanograins

Making small nanograins in polycrystalline organic-inorganic halide perovskite (OIHP) films is critical to improving the luminescent efficiency in perovskite light-emitting diodes (PeLEDs). 3D polycrystalline OIHPs have fundamental limitations related to exciton binding energy and exciton diffusion length. At the same time, passivating the defects at the grain boundaries is also critical when the grain size becomes smaller. Molecular additives can be incorporated to shield the nanograins to suppress defects at grain boundaries; however, unevenly distributed molecular additives can cause imbalanced charge distribution and inefficient local defect passivation in polycrystalline OIHP films. Here, a kinetically controlled polycrystalline organic-shielded nanograin (OSN) film with a uniformly distributed organic semiconducting additive (2,2 ',2 ''-(1,3,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole), TPBI) is developed mimicking core-shell nanoparticles. The OSN film causes improved photophysical and electroluminescent properties with improved light out-coupling by possessing a low refractive index. Finally, highly improved electroluminescent efficiencies of 21.81% ph el(-1) and 87.35 cd A(-1) are achieved with a half-sphere lens and four-time increased half-lifetime in polycrystalline PeLEDs. This strategy to make homogeneous, defect-healed polycrystalline core-shell-mimicked nanograin film with better optical out-coupling will provide a simple and efficient way to make highly efficient perovskite polycrystal films and their optoelectronics devices.

Novel Ni–Co-based superalloys with high thermal stability and specific yield stress discovered by directed energy deposition

We report on the rapid alloy screening of Ni–Co–Ti–Al–Mo superalloys with high thermal stability and specific yield stress by means of directed energy deposition. A laser directed energy deposition, a specific type of additive manufacturing, was employed using multiple powder feeders and elemental powders. Fifty superalloys of different compositions were deposited and the heat-treated microstructure and γ' solvus temperature were examined. The 43Ni–38Co–9Ti–6Al–4Mo superalloy (atomic percent composition) exhibited a uniform γ/γ' microstructure and a γ' solvus temperature of 1202°C. The beneficial properties of the superalloy were also found in the cast superalloy of identical composition. The cast superalloy exhibited a thermally stable γ/γ' microstructure with cuboidal γ' precipitates even after long-term aging heat treatments at 800°C, 900°C, and 1000°C up to 500 h. The γ'-coarsening mechanism was evaluated based on the Lifshitz–Slyozov–Wagner model and the trans-interface diffusion-controlled model. A transition between these two mechanisms was observed with an increase in aging temperature. Atom probe tomography analyses revealed that the sluggish interface diffusion of Co and corresponding reduction of the interfacial energy induced the transition of the γ'-coarsening mechanism. Moreover, the cast superalloy showed an enhanced specific yield stress attributed to its exceptionally low alloy density of 7.61 g/cm3

Association between severe hepatic steatosis examined by Fibroscan and the risk of high-risk colorectal neoplasia.

The prevalence of colorectal neoplasm in patients with non-alcoholic fatty liver disease has increased twice as high as that in the general population. FibroScan is a new modality for evaluating hepatic steatosis. This study aimed to investigate the relationship between the risk of high-risk colorectal neoplasia and hepatic steatosis examined using FibroScan. This was a cross sectional study of prospectively enrolled subjects who were scheduled to undergo index colonoscopy as a health screening between March 2018 and February 2019. The severity of steatosis was graded as normal, mild, moderate, or severe using FibroScan. A total of 140 consecutive subjects were enrolled and sequentially examined using FibroScan and colonoscopy. Subjects with hepatic steatosis had more high-risk colorectal neoplasia than those without hepatic steatosis. In addition, tumor size was larger in subjects with hepatic steatosis. In multivariable analysis, severe hepatic steatosis was an independent risk factor for high-risk colorectal neoplasia (adjusted odds ratio: 3.309, confidence interval: 1.043-10.498, p = 0.042). Alcohol consumption was also identified as a risk factor for high-risk colorectal neoplasia. In conclusion, severe hepatic steatosis on FibroScan is associated with the development of high-risk colorectal neoplasia. Thus, physicians should be aware of the association between colorectal neoplasia and hepatic steatosis assessed by FibroScan and its clinical implications

Solution-Processed Hole-Doped SnSe Thermoelectric Thin-Film Devices for Low-Temperature Power Generation

Owing to the increase in the demand for energy autonomy in electronic systems, there has been increased research interest in thermoelectric thin-film-based energy harvesters. However, the fabrication of such devices is challenging when considering material performance and integration processes. SnSe has emerged as among the best bulk thermoelectric materials capable of functioning at high temperatures; however, the thermoelectric performance of thin films is still limited. Herein, we present a solution-processed fabrication of high-performance Ag-doped SnSe thin films operable in a low-temperature range. The Ag doping induces the preferred crystallographic orientation and grain growth in the b-c plane (in-plane) of SnSe, consequently enhancing thermoelectric performance at low temperatures. Moreover, thin-film wrinkling and photolithography are employed in the fabrication of stretchable and patterned devices, in which power generation performance is then evaluated, thereby demonstrating the feasibility of the proposed thin films as an energy harvester in emerging electronic systems

Soluble Telluride-Based Molecular Precursor for Solution-Processed High-Performance Thermoelectrics

The recent interest in wearable electronics suggests flexible thermoelectrics as candidates for the power supply. Herein, we report a solution process to fabricate flexible Sb2Te3 thermoelectric thin films using molecular Sb2Te3 precursors, synthesized by the reduction of Sb2Te3 powder in ethylenediamine and ethanedithiol with superhydride. The fabricated flexible Sb2Te3 thin films exhibit a power factor of ???8.5 ??W cm???1 K???2 at 423 K, maintaining the properties during 1000 bending cycles. FePt nanoparticles are homogeneously embedded in the Sb2Te3 thin film, reducing the thermal conductivity. The current study offers considerable potential for manufacturing high-performance flexible thin film devices