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The electrochemical formation of liquid sulfur at room temperature on the basal plane of MoS

Two-dimensional Ruddlesden-Popper perovskites (RPPs) with multiple quantum well-like structures, strong excitonic quantum confinement, and high stability are promising optical gain media. However, the lasing from such material with a small number of inorganic well layers is difficult to achieve. Herein, we demonstrate the low-threshold upconversion lasing from the homologous RPP (PEA)

Metal halide perovskites are emerging materials for next-generation optoelectronic devices, of which the all-inorganic CsPbBr3 perovskite has attracted increasing attention due to its outstanding stability and excellent photoelectric characteristics compared with organic–inorganic counterparts. However, the electroluminescence (EL) efficiencies of inorganic CsPbBr3 perovskite light-emitting diodes (PeLEDs) are unsatisfactory because of high trap densities, which lead to non-radiative recombination loss. Herein, by introducing potassium bromide (KBr), we successfully prepare zero-dimensional/three-dimensional (0D/3D) Cs4−xKxPbBr6/CsPbBr3 heterostructure perovskite films with suppressed trap density and improved photoluminescence quantum yield (PLQY). The deep energy level of 0D Cs4−xKxPbBr6 phase is confirmed using DFT calculation. Moreover, the formation of the unique heterostructure inhibits the free charge diffusion at the grain boundary from suffering trapping and recombination, which facilitates efficient radiative recombination in the 3D CsPbBr3 phase. Therefore, the optimized green PeLEDs show a high external quantum efficiency (EQE) of 12.8%, which is a six-fold improvement over the pristine one (2.1%), and a maximum brightness of 39 400 cd m−2. Our work provides a rational charge carrier confinement strategy for developing high-performance PeLEDs and can be broadened to other potential perovskite materials, not restricted to the CsPbBr3-based perovskite films.

Work function strongly impacts the surficial charge distribution, especially for metal-support electrocatalysts when a built-in electric field (BEF) is constructed. Therefore, studying the correlation between work function and BEF is crucial for understanding the intrinsic reaction mechanism. Herein, we present a Pt@CoOx electrocatalyst with a large work function difference (ΔΦ) and strong BEF, which shows outstanding hydrogen evolution activity in a neutral medium with a 4.5-fold mass activity higher than 20 % Pt/C. Both experimental and theoretical results confirm the interfacial charge redistribution induced by the strong BEF, thus subtly optimizing hydrogen and hydroxide adsorption energy. This work not only provides fresh insights into the neutral hydrogen evolution mechanism but also proposes new design principles toward efficient electrocatalysts for hydrogen production in a neutral medium. Agency for Science, Technology and Research (A*STAR) This work was financially supported by the Research Grants Council of Hong Kong (Poly U253009/18P) and the Hong Kong Polytechnic University (1-ZVGH). H.J.F. thanks the financial support from Agency for Science, Technology, and Research (A*STAR), Singapore by AME Individual Research Grants (A1983c0026).

Single crystal scintillators of RE2O3:Eu (RE = Lu, Y, Sc) with high (8%) and low (1%) Eu doping concentration were grown by the optical floating zone method. The luminescence and scintillation properties have been investigated and compared thoroughly. Correlated measurements of afterglow curves, photoluminescence excitation and photoluminescence, photoluminescence decay curves and X-ray excitation curves were performed. Lu2O3:Eu and Y2O3:Eu present significant afterglow intensity decreasing after high Eu concentration doping. While for the Sc2O3:Eu, its afterglow intensity even increases slightly. The luminescence efficiencies of high doping concentration samples are weaker than that of the low concentration ones due to the concentration quenching. The integrated X-ray excitation luminescence reveals the scintillation luminescence efficiencies of samples with the high concentration or the low ones both have the following sequence:Lu2O3:Eu＞Y2O3:Eu＞Sc2O3:Eu.