Electromagnetic (EM) absorbers play an increasingly essential role in electronic information age, even towards coming intelligent life. The remarkable merits of heterointerface engineering and its peculiar EM characteristics inject a fresh and infinite vitality to design high-efficiency and stimuli-responsive EM absorbers. However, there still exist huge challenges in understanding and reinforcing these interface effects from the micro and macro perspectives. Herein, the EM response mechanisms of interfacial effects are dissected in depth, and advanced characterization as well as theoretical techniques is highly focused on. Then, the representative optimization strategies are systematically discussed with an emphasis on component selection and structural design. More importantly, the most cutting-edge smart EM functional devices based on heterointerface engineering are reported as highlights. Finally, current challenges and concrete suggestion are proposed, and future perspectives on this promising field are predicted as well. This article is protected by copyright. All rights reserved.

Heterointerface Engineering in Electromagnetic Absorbers: New Insights and Opportunities

Sign language recognition, especially the sentence recognition, is of great significance for lowering the communication barrier between the hearing/speech impaired and the non-signers. The general glove solutions, which are employed to detect motions of our dexterous hands, only achieve recognizing discrete single gestures (i.e., numbers, letters, or words) instead of sentences, far from satisfying the meet of the signers’ daily communication. Here, we propose an artificial intelligence enabled sign language recognition and communication system comprising sensing gloves, deep learning block, and virtual reality interface. Non-segmentation and segmentation assisted deep learning model achieves the recognition of 50 words and 20 sentences. Significantly, the segmentation approach splits entire sentence signals into word units. Then the deep learning model recognizes all word elements and reversely reconstructs and recognizes sentences. Furthermore, new/never-seen sentences created by new-order word elements recombination can be recognized with an average correct rate of 86.67%. Finally, the sign language recognition results are projected into virtual space and translated into text and audio, allowing the remote and bidirectional communication between signers and non-signers. Though wearable gloves are widely used for gesture associated applications (e.g. sign language recognition), sentence identification of sign language remains a challenge. Here, the authors report AI-enabled recognition system helps barrier-free communication between signers and non-signers.

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AI enabled sign language recognition and VR space bidirectional communication using triboelectric smart glove.

Lightweight and flexible self-charging power systems with synchronous energy harvesting and energy storage abilities are highly desired in the era of the internet of things and artificial intelligences, which can provide stable, sustainable, and autonomous power sources for ubiquitous, distributed, and low-power wearable electronics. However, there is a lack of comprehensive review and challenging discussion on the state-of-the-art of the triboelectric nanogenetor (TENG)-based self-charging power textiles, which have a great possibility to become the future energy autonomy power sources. Herein, the recent progress of the self-charging power textiles hybridizing fiber/fabric based TENGs and fiber/fabric shaped batteries/supercapacitors is comprehensively summarized from the aspect of textile structural designs. Based on the current research status, the key bottlenecks and brighter prospects of self-charging power textiles are also discussed in the end. It is hoped that the summary and prospect of the latest research of self-charging power textiles can help relevant researchers accurately grasp the research progress, focus on the key scientific and technological issues, and promote further research and practical application process.

Self-charging power textiles integrating energy harvesting triboelectric nanogenerators with energy storage batteries/supercapacitors

Triboelectric bending sensor based smart glove towards intuitive multi-dimensional human-machine interfaces

Anion exchange membrane water electrolysis (AEMWE) with non-precious catalysts offers a promising route for industrial hydrogen production. However, the sluggish kinetics of anodic water oxidation hinder its efficiency and cost. We report herein a highly active two-dimensional trimetal–organic framework (NiCoFe–NDA) as a referential electrocatalyst for water oxidation. The as-prepared NiCoFe–NDA delivers a low overpotential of 215 mV at 10 mA cm−2 with a small Tafel slope of 64.1 mV dec−1 and exhibits excellent stability even at a high current density of 100 mA cm−2 for 50 h without obvious activity attenuation. A home-made AEMWE using an anodic NiCoFe–NDA catalyst affords a cell voltage of only 1.8 V to drive a current density of 325 mA cm−2 and performs robustly during continuous operation for over 100 h. During the anodic water oxidation, NiCoFe–NDA undergoes an in situ phase transformation, and the surface-reconstructed NiCoFe–NDA inherits its topological nanosheets and induces active surface-rich metal oxyhydroxides with abundant low-coordination catalytic environments, which would provide a positive multi-metal coupling effect to promote water oxidation. This work provides an organic–inorganic hybrid platform for designing high-efficiency electrocatalysts to advance water electrolysis technologies.

In situ ion-exchange preparation and topological transformation of trimetal–organic frameworks for efficient electrocatalytic water oxidation

Application of two-dimensional MXene materials in photovoltaics has attracted increasing attention since the first report in 2018 due to their metallic electrical conductivity, high carrier mobility, excellent transparency, tunable work function and superior mechanical property. In this review, all developments and applications of the Ti3C2Tx MXene (here, it is noteworthy that there are still no reports on other MXenes’ application in photovoltaics by far) as additive, electrode and hole/electron transport layer in solar cells are detailedly summarized, and meanwhile, the problems existing in the related studies are also discussed. In view of these problems, some suggestions are given for pushing exploration of the MXenes’ application in solar cells. It is believed that this review can provide a comprehensive and deep understanding into the research status and, moreover, helps widen a new situation for the study of MXenes in photovoltaics.

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MXenes for Solar Cells

The electric-field effect is an important factor to enhance the charge diffusion and transfer kinetics of interfacial electrode materials. Herein, by designing a heterojunction, the influence of the electric-field effect on the kinetics of the MoS2 as cathode materials for aqueous Zn-ion batteries (AZIBs) is deeply investigated. The hybrid heterojunction is developed by hydrothermal growth of MoS2 nanosheets on robust titanium-based transition metal compound ([titanium nitride, TiN] and [titanium oxide, TiO2 ]) nanowires, denoted TNC@MoS2 and TOC@MoS2 NWS, respectively. Benefiting from the heterostructure architecture and electric-field effect, the TNC@MoS2 electrodes exhibit an impressive rate performance of 200 mAh g-1 at 50 mA g-1 and cycling stability over 3000 cycles. Theoretical studies reveal that the hybrid architecture exhibits a large-scale electric-field effect at the interface between TiN and MoS2 , enhances the adsorption energy of Zn-ions, and increases their charge transfer, which leads to accelerated diffusion kinetics. In addition, the electric-field effect can also be effectively applied to TiO2 and MoS2 , confirming that the concept of heterostructures stimulating electric-field can provide a relevant understanding for the architecture of other cathode materials for AZIBs and beyond.

Heterostructures Stimulate Electric-Field to Facilitate Optimal Zn2+ Intercalation in MoS2 Cathode.

Improved comprehensive performance of CsPbI2Br perovskite solar cells by modifying the photoactive layers with carbon nanodots

CsPbI2Br is promising in the application of perovskite solar cells (PSCs) owing to its reasonable bandgap and good thermal stability. However, the reported power conversion efficiency (PCE) of the CsPbI2Br solar cells is still much lower than that of the organic-inorganic hybrid PSCs, mainly due to relatively poor CsPbI2Br crystal quality. Herein, additive engineering to the photoactive layer of CsPbI2Br using the Ti3C2Tx MXene nanosheets is reported. Thanks to the improved crystallinity/reduced defect density, together with the formation of the Schottky junction between the MXene nanosheets and CsPbI2Br, enhanced separation and transfer of the photogenerated electron-hole pairs can be achieved for optimal MXene addition. A simple device configuration of ITO/SnO2/Ti3C2Tx-added CsPbI2Br/P3HT/Ag can thus deliver a significantly boosted PCE of 15.10%, i.e., a ∼16.69% relative increment compared with that (12.94%) of the control device without adding MXene. In addition, the enhanced humidity resistance is achieved for the MXene-added CsPbI2Br layers.

Improved Comprehensive Photovoltaic Performance and Mechanisms by Additive Engineering of Ti3C2Tx MXene into CsPbI2Br.

In this study, a novel photovoltaic cell based on the Ti3C2Tx MXene/n-type silicon (n-Si) Schottky junction is developed by a simple solution-processed method of drop-casting the Ti3C2Tx MXene ethanol suspension onto the surface of n-Si wafers and the subsequent natural drying in air. The demonstration device with a simple configuration of Ag (top electrode)/Ti3C2Tx/n-Si/In:Ga (back electrode) delivers a power conversion efficiency (PCE) of 5.70% with a short-circuit current density (Jsc) of 20.68 mA cm−2, open-circuit voltage (Voc) of 0.530 V and fill factor (FF) of 52.0% under AM 1.5G illumination. After treating the MXene layer with the SnCl2 aqueous solution, an improved PCE to 6.95% (Jsc: 23.04 mA cm−2; Voc: 0.536 V; FF: 56.2%) can be achieved because of the reduced light reflection, improved quality of junction and electrical contact, as well as the increased carrier lifetime/suppressed carrier recombination. Given the simple device configuration, facile preparation and huge potential for performance improvement, this work is believed to provide valuable exploration of developing novel solar cells.

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Xincheng Yao

Papers

MXenes for Solar Cells

Heterostructures Stimulate Electric-Field to Facilitate Optimal Zn2+ Intercalation in MoS2 Cathode.

Improved comprehensive performance of CsPbI2Br perovskite solar cells by modifying the photoactive layers with carbon nanodots

Improved Comprehensive Photovoltaic Performance and Mechanisms by Additive Engineering of Ti3C2Tx MXene into CsPbI2Br.

Solution-processed silicon/SnCl2-treated Ti3C2Tx MXene Schottky junction solar cells