Polymer‐Based Low‐Temperature Thermoelectric Composites

AbstractThermoelectric materials allow direct conversion of waste heat energy into electrical energy, thus contributing to solving energy related issues. Polymer‐based materials have been considered for use in heat conversion in the temperature range from 20 to 200 °C, within which conventional materials are not efficient enough, whereas polymers due to their good electronic transport properties, easy processability, non‐toxicity, flexibility, abundance, and simplicity of adjustment, are considered as promising materials. Due to the large variety of available polymers and the almost unlimited combinations of possible modifications, the field of polymer‐based thermoelectrics is very rapidly developing, already reaching efficiency values close to those of inorganic systems. In the current progress report, the most recent advances in the field are discussed. New approaches to improve thermoelectric performance are described, with a focus on revising the mechanisms to improve the thermoelectric properties of the three most investigated polymer matrixes: poly(3,4‐ethylenedioxythiophene) polystyrene sulfonat, poly(3‐hexylthiophene‐2,5‐diyl), and polyaniline, alongside the three main paths of optimizing properties: incorporation of carbon‐based material and inorganic substances, and treatment with chemical agents. The most promising research in the field is highlighted and thoroughly analyzed. The path toward a lab‐to‐fab transition for thermoelectric polymers is suggested in perspective

Enhanced Mechanical, Thermal and Electrical Properties of High-Entropy HfMoNbTaTiVWZr Thin Film Metallic Glass and its Nitrides

The inception of high-entropy alloy promises to push the boundaries for new alloy design with unprecedented properties. This work reports entropy stabilisation of an octonary refractory, HfMoNbTaTiVWZr, high-entropy thin film metallic glass, and derived nitride films. The thin film metallic glass exhibited exceptional ductility of approximate to 60% strain without fracture and compression strength of 3 GPa in micro-compression, due to the presence of high density and strength of bonds. The thin film metallic glass shows thermal stability up to 750 degrees C and resistance to Ar-ion irradiation. Nitriding during film deposition of HfMoNbTaTiVWZr thin film of strong nitride forming refractory elements results in deposition of nanocrystalline nitride films with compressive strength, hardness, and thermal stability of up to 10 GPa, 18.7 GPa, and 950 degrees C, respectively. The high amount of lattice distortion in the nitride films leads to its insulating behaviour with electrical conductivity as low as 200 S cm(-1) in the as-deposited film. The design and exceptional properties of the thin film metallic glass and derived nitride films may open up new avenues of development of bulk metallic glasses and the application of refractory-based high entropy thin films in structural and functional applications

Facile synthesis of solid-state fluorescent organosilica nanoparticles with a photoluminescence quantum yield of 73.3% for fingerprint recognition and white-light-emitting diodes

Polymer-like coated OSiNPs with a solid-state PLQY of up to 73.3% for applications in WLEDs and fingerprint recognition are fabricated by a simple hydrothermal method

Ag-sensitized Tb3+/Yb3+ codoped silica-zirconia glasses and glass-ceramics: Systematic and detailed investigation of the broadband energy-transfer and downconversion processes

Abstract Various studies report that Tb3+/Yb3+ co-doped materials can split one UV or 488 nm (visible) photon in two near infrared (NIR) photons at 980 nm by an energy-transfer process involving one Tb3+ and two Yb3+ ions. Additionally, it was demonstrated that Ag multimers can provide an efficient optical sensitizing effect for rare earth ions (RE3+ ions), resulting in a broadband enhanced excitation, which could have a significant technological impact, overcoming their limited spectral absorptions and small excitation cross sections. However, a systematic and detailed investigation of the down-conversion process enhanced by Ag nanoaggregates is still lacking, which is the focus of this paper. Specifically, a step by step analysis of the energy-transfer quantum-cutting chain in Ag-exchanged Tb3+/Yb3+ co-doped glasses and glass-ceramics is presented. Moreover, the direct Ag-Yb3+ energy-transfer is also considered. Results of structural, compositional, and optical characterizations are given, providing quantitative data for the efficient broadband Ag-sensitization of Tb3+/Yb3+ quantum cutting. A deeper understanding of the physical processes beneath the optical properties of the developed materials will allow a wiser realization of more efficient energy-related devices, such as spectral converters for silicon solar cells and light-emitting devices (LEDs) in the visible and NIR spectral regions

Engineering high-emissive silicon-doped carbon nanodots towards efficient large-area luminescent solar concentrators

Luminescent solar concentrators (LSCs) are devices that can collect sunlight from a large area, concentrating it at the borders of the slab, to achieve efficient photovoltaic conversion when small area solar cells are placed at their edges, realizing building-integrated photovoltaics. Efficient luminophores in terms of high luminescence quantum yield are needed to obtain high-performance LSCs. A key point is the ability to engineer the Stokes shift (i.e. the difference between the maximum of the absorption and emission spectra), to minimize reabsorption processes. In this work, we report novel silicon-doped carbon nanodots (Si-CDs) with an ultrahigh quantum yield (QY) up to 92.3% by a simple hydrothermal method. Thin-film structured LSCs (5 × 5 × 0.2 cm3) with different concentrations of Si-CDs are prepared by dispersing the Si-CDs into polyvinyl pyrrolidone (PVP) matrix, and the optimal power conversion efficiency (PCE) of LSCs can be as high as 4.36%, which is nearly 2.5 times higher than that prepared with silicon-undoped CDs. This Si-CDs/PVP film LSC has a high QY of 80.5%. A large-area LSC (15 × 15 cm2) is also successfully fabricated, which possesses a PCE of 2.06% under natural sunlight irradiation (35 mW·cm−2), one of the best reported values for similar size LSCs. The efficient Si-CDs as luminescent substances for high-efficiency large-area LSCs will further give an impetus to the practical exploitation of LSCs

Controllable Synthesis of 2D Nonlayered Cr2S3 Nanosheets and Their Electrocatalytic Activity Toward Oxygen Evolution Reaction

The design of oxygen evolution reaction (OER) electrocatalysts based on Earth-abundant materials holds great promise for realizing practically viable water-splitting systems. In this regard, two-dimensional (2D) nonlayered materials have received considerable attention in recent years owing to their intrinsic dangling bonds which give rise to the exposure of unsaturated active sites. In this work, we solved the synthesis challenge in the development of a 2D nonlayered Cr2S3 catalyst for OER application via introducing a controllable chemical vapor deposition scheme. The as-obtained catalyst exhibits a very good OER activity requiring overpotentials of only 230 mV and 300 mV to deliver current densities of 10 mA cm−2 and 30 mA cm−2 , respectively, with robust stability. This study provides a general approach to optimize the controllable growth of 2D nonlayered material and opens up a fertile ground for studying the various strategies to enhance the water splitting reaction

Luminescent Cu(I) complex with bis(indazol-1-yl)phenylmethane as chelating ligand

The cationic Cu(I) complex [Cu(N^N)2]+, where N^N is bis(indazol-1-yl)phenylmethane, was synthesized as chloride or tetrafluoroborate salt by reacting CuCl or [Cu(NCCH3)4][BF4] with bis(indazol-1-yl)phenylmethane under mild conditions. The structure of [Cu(N^N)2]Cl was ascertained by single-crystal X-ray diffraction. The complex exhibited bright yellow emission upon excitation with near UV and violet light, attributed to triplet LLCT/MLCT transitions on the basis of experimental data and computational outcomes

functionalized multi wall carbon nanotubes tio2 composites as efficient photoanodes for dye sensitized solar cells

The incorporation of functionalized multi-wall carbon nanotubes into TiO2 mesoporous photoanodes for dye-sensitized solar cells leads to 30% enhancement in photoconversion efficiency of the optimized system

Synergistic tailoring of band structure and charge carrier extraction in "green" core/shell quantum dots for highly efficient solar energy conversion

Environment-friendly colloidal core/shell quantum dots (QDs) with controllable optoelectronic characteristics are promising building blocks for future commercial solar technologies. Herein, we synergistically tailor the electronic band structure and charge carrier extraction of eco-friendly AgInS2 (AIS)/ZnS core/shell QDs via Mn-alloying and Cu-doping in the core and shell, respectively. It is demonstrated that the Mn-alloying in AIS core can broaden the band gap to facilitate delocalization of photogenerated electrons into the shell and further incor-poration of Cu in the ZnS shell enables the creation of Cu-related states that capture the photogenerated holes from core, thus leading to charge carrier recombination and accelerated transfer of photogenerated electrons in the core/shell QDs. As-prepared Mn-AIS/ZnS@Cu QDs were assembled as light harvesters in a photo-electrochemical (PEC) device for light-driven hydrogen evolution, delivering a maximum photocurrent density of ~ 6.4 mA cm-2 with superior device stability under standard one sun irradiation (AM 1.5G, 100 mW cm(-2)). Our findings highlight that simultaneously engineering the band alignment and charge carrier dynamics of "green " core/shell QDs endow the feasibility to design future high-efficiency and durable solar hydrogen pro-duction systems

Enhanced Mechanical, Thermal and Electrical Properties of High-Entropy HfMoNbTaTiVWZr Thin Film Metallic Glass and its Nitrides

The inception of high-entropy alloy promises to push the boundaries for new alloy design with unprecedented properties. This work reports entropy stabilisation of an octonary refractory, HfMoNbTaTiVWZr, high-entropy thin film metallic glass, and derived nitride films. The thin film metallic glass exhibited exceptional ductility of approximate to 60% strain without fracture and compression strength of 3 GPa in micro-compression, due to the presence of high density and strength of bonds. The thin film metallic glass shows thermal stability up to 750 degrees C and resistance to Ar-ion irradiation. Nitriding during film deposition of HfMoNbTaTiVWZr thin film of strong nitride forming refractory elements results in deposition of nanocrystalline nitride films with compressive strength, hardness, and thermal stability of up to 10 GPa, 18.7 GPa, and 950 degrees C, respectively. The high amount of lattice distortion in the nitride films leads to its insulating behaviour with electrical conductivity as low as 200 S cm(-1) in the as-deposited film. The design and exceptional properties of the thin film metallic glass and derived nitride films may open up new avenues of development of bulk metallic glasses and the application of refractory-based high entropy thin films in structural and functional applications