Flexible thermoelectrics is a synergy of flexible electronics and thermoelectric energy conversion. In this work, we fabricated flexible full-inorganic thermoelectric power generation modules based on doped silver chalcogenides.

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Tuning metal–support interaction has been considered as an effective approach to modulate the electronic structure and catalytic activity of supported metal catalysts. At the atomic level, the understanding of the structure–activity relationship still remains obscure in heterogeneous catalysis, such as the conversion of water (alkaline) or hydronium ions (acid) to hydrogen (hydrogen evolution reaction, HER). Here, we reveal that the fine control over the oxidation states of single-atom Pt catalysts through electronic metal–support interaction significantly modulates the catalytic activities in either acidic or alkaline HER. Combined with detailed spectroscopic and electrochemical characterizations, the structure–activity relationship is established by correlating the acidic/alkaline HER activity with the average oxidation state of single-atom Pt and the Pt–H/Pt–OH interaction. This study sheds light on the atomic-level mechanistic understanding of acidic and alkaline HER, and further provides guidelines for the rational design of high-performance single-atom catalysts.

Advances in perovskite solar cells require development of means to control and eliminate the nonradiative charge recombination pathway. Using ab initio nonadiabatic molecular dynamics, we demonstrate that charge recombination in perovskites is extremely sensitive to the charge state of the halogen vacancy. A missing iodine anion in MAPbI3 has almost no effect on charge losses. However, when the vacancy is reduced, the recombination is accelerated by up to 2 orders of magnitude. The acceleration occurs due to formation of a deep hole trap in the singly reduced vacancy, and both deep and shallow hole traps for the doubly reduced vacancy. The shallow hole involves a significant rearrangement of the Pb–I lattice, leading to a new chemical species: a Pb–Pb dimer bound by the vacancy charge, and under-coordinated iodine bonds. Hole trapping by the singly reduced iodide vacancy operates parallel to recombination of free electron and hole, accelerating charge losses by a factor of 5. The doubly reduced vacancy acts by a sequential mechanism-free hole, to shallow trap, to deep trap, to free electron, and accelerates the recombination by a factor of 50. The study demonstrates that iodine anion vacancy can be beneficial to the performance, because it causes minor changes to the charge carrier lifetime, while increasing charge carrier concentration. However, the neutral iodine and iodine cation vacancies should be strongly avoided. The detailed insights into the charge carrier trapping and relaxation mechanisms provided by the simulation are essential for development of efficient photocatalytic, photovoltaic, optoelectronic and related devices.

BaZrS3 is a prototypical chalcogenide perovskite, an emerging class of unconventional semiconductor. Recent results on powder samples reveal that it is a material with a direct band gap of 1.7-1.8 eV, a very strong light-matter interaction, and a high chemical stability. Due to the lack of quality thin films, however, many fundamental properties of chalcogenide perovskites remain unknown, hindering their applications in optoelectronics. Here we report the fabrication of BaZrS3 thin films, by sulfurization of oxide films deposited by pulsed laser deposition. We show that these films are n-type with carrier densities in the range of 10 19 -10 20 cm -3 . Depending on the processing temperature, the Hall mobility ranges from 2.1 to 13.7 cm 2 /Vs. The absorption coefficient is > 10 5 cm -1 at photon energy > 1.97 eV. Temperature dependent conductivity measurements suggest shallow donor levels. By assuring that BaZrS3 is a promising candidate, these results potentially unleash the family of chalcogenide perovskites for optoelectronics such as photodetectors, photovoltaics, and light emitting diodes.

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Zigzag edges of monolayer MoS2 and other transition-metal (TM) dichalcogenides are experimentally shown to exhibit strong photoluminescence. Atomic models that have been proposed for these edges, however, are all metallic. Here, we address this puzzle by using first-principles calculations. We found that a more generic electron counting model (ECM) can be developed, which, when coupled with the ability of TM atoms at edges to change their valency from 4+ to 5+, can quantitatively account for the band gap opening at the zigzag edges. Due to the ECM, a 3× periodicity along the zigzag edge is necessary to open the band gap. Moreover, consistent with experiment, oxygen adsorption is shown to open even larger band gaps than intrinsic edges.

The platinum single‐atom‐catalyst is verified as a very successful route to approach the size limit of Pt catalysts, while how to further improve the catalytic efficiency of Pt is a fundamental scientific question and is challenging because the size issue of Pt is approached at the ultimate ceiling as single atoms. Here, a new route for further improving Pt catalytic efficiency by cobalt (Co) and Pt dual‐single‐atoms on titanium dioxide (TiO2) surfaces, which contains a fraction of nonbonding oxygen‐coordinated Co–O–Pt dimers, is reported. These Co–Pt dimer sites originate from loading high‐density Pt single‐atoms and Co single‐atoms, with them anchoring randomly on the TiO2 substrate. This dual‐single‐atom catalyst yields 13.4% dimer sites and exhibits an ultrahigh and stable photocatalytic activity with a rate of 43.467 mmol g−1 h−1 and external quantum efficiency of ≈83.4% at 365 nm. This activity far exceeds those of equal amounts of Pt single‐atom and typical Pt clustered catalysts by 1.92 and 1.64 times, respectively. The enhancement mechanism relies on the oxygen‐coordinated Co–O–Pt dimer coupling, which can mutually optimize the electronic states of both Pt and Co sites to weaken H* binding. Namely, the “mute” Co single‐atom is activated by Pt single‐atom and the activity of the Pt atom is further enhanced through the dimer interaction. This strategy of nonbonding interactive dimer sites and the oxygen‐mediated catalytic mechanisms provide emerging rich opportunities for greatly improving the catalytic efficiency and developing novel catalysts with creating new electronic states.