SnSe emerges as a new class of thermoelectric materials since the recent discovery of an ultrahigh thermoelectric figure of merit in its single crystals. Achieving such performance in the polycrystalline counterpart is still challenging and requires fundamental understandings of its electrical and thermal transport properties as well as structural chemistry. Here we demonstrate a new strategy of improving conversion efficiency of bulk polycrystalline SnSe thermoelectrics. We show that PbSe alloying decreases the transition temperature between Pnma and Cmcm phases and thereby can serve as a means of controlling its onset temperature. Along with 1% Na doping, delicate control of the alloying fraction markedly enhances electrical conductivity by earlier initiation of bipolar conduction while reducing lattice thermal conductivity by alloy and point defect scattering simultaneously. As a result, a remarkably high peak ZT of ∼1.2 at 773 K as well as average ZT of ∼0.5 from RT to 773 K is achieved for Na(SnPb)Se. Surprisingly, spherical-aberration corrected scanning transmission electron microscopic studies reveal that NaSnPbSe (0 < x ≤ 0.2; y = 0, 0.01) alloys spontaneously form nanoscale particles with a typical size of ∼5-10 nm embedded inside the bulk matrix, rather than solid solutions as previously believed. This unexpected feature results in further reduction in their lattice thermal conductivity.

The discovery of SnSe single crystals with record high thermoelectric efficiency along the b-axis has led to the search for ways to synthesize polycrystalline SnSe with similar efficiencies. However, due to weak texturing and difficulties in doping, such high thermoelectric efficiencies have not been realized in polycrystals or thin films. Here, we show that highly textured and hole doped SnSe thin films with thermoelectric power factors at the single crystal level can be prepared by solution process. Purification step in the synthetic process produced a SnSe-based chalcogenidometallate precursor, which decomposes to form the SnSe2 phase. We show that the strong textures of the thin films in the b–c plane originate from the transition of two dimensional SnSe2 to SnSe. This composition change-driven transition offers wide control over composition and doping of the thin films. Our optimum SnSe thin films exhibit a thermoelectric power factor of 4.27 μW cm−1 K−2.

The higher catalytic activity and stability for a gas-phase carbonylation of dimethyl ether (DME) to methyl acetate (MA) on the seed-derived ferrierite (FER) were attributed to its higher crystallinity with small amounts of defect sites by recrystallization methods without using any organic structure directing agent. The recrystallized FER (FER-S1) with its smaller amount of Lewis acidic extraframework Al sites (EFAl) possessed proper number of Brønsted acidic sites in the eight-membered-ring (8-MR) channels in comparison to the pristine FER, which was responsible for an enhanced CO insertion rate to methoxy intermediates formed by dissociated DME molecules by referentially forming acetyl intermediates or to the highly active Brønsted acidic sites. The most active tetrahedral T2 sites with two adjacent Al atoms in the 8-MR channels having next-nearest Al–O–Si–O–Al configurations on the FER-S1 revealed the stronger adsorption of the stably adsorbed DME molecules as confirmed by DFT calculations. FER-S1 containing the proper amounts of Al atoms in the 8-MR with appropriate locations with optimal acidic properties was responsible for its higher activity and stability for the gas-phase carbonylation of DME, where the Al distributions were confirmed by Rietveld refinement XRD analysis, FT-IR, and DFT calculations. In addition, the acidic sites on the outer surfaces and larger cavity including 10-MR channels were responsible for an accelerated formation of aromatic coke precursors.

The first-principle modeling of heterogeneous catalysts is a revolutionarily approach, as the electronic structure of a catalyst is closely related to its reactivity on the surface with reactant molecules. In the past, detailed reaction mechanisms could not be understood, however, computational chemistry has made it possible to analyze a specific elementary reaction of a reaction system. Microkinetic modeling is a powerful tool for investigating elementary reactions and reaction mechanisms for kinetics. Using a microkinetic model, the dominant pathways and rate-determining steps can be elucidated among the competitive reactions, and the effects of operating conditions on the reaction mechanisms can be determined. Therefore, the combination of computational chemistry and microkinetic modeling can significantly improve computational catalysis research. In this study, we reviewed the trends and outlook of this combination technique as applied to the catalytic synthesis of methanol (MeOH) and dimethyl ether (DME), whose detailed mechanisms are still controversial. Although the scope is limited to the catalytic synthesis of limited species, this study is expected to provide a foundation for future works in the field of catalysis research based on computational catalysis.

We have demonstrated that the sequential lateral solidification (SLS) technology can be utilized for the large area AMOLED. An optimized SLS process provides us with polycrystalline Si films with well‐controlled grain size and location. The thin film transistors (TFTs) with SLS‐processed Si films show high performance with desirable uniformity. 14″ WXGA (1280×RGB×768) AMOLEDs were fabricated with SLS‐processed TFT backplanes. We utilized RGB evaporation process with fine metal mask. The novel delta pixel arrangement results in increased aperture ratio and wider FMM process window. The advantage of SLS process will be discussed.