Lightweight, ultrathin, and flexible electromagnetic interference (EMI) shielding materials are needed to protect electronic circuits and portable telecommunication devices and to eliminate cross-talk between devices and device components. Here, we show that a two-dimensional (2D) transition metal carbonitride, Ti3CNTx MXene, with a moderate electrical conductivity, provides a higher shielding effectiveness compared with more conductive Ti3C2Tx or metal foils of the same thickness. This exceptional shielding performance of Ti3CNTx was achieved by thermal annealing and is attributed to an anomalously high absorption of electromagnetic waves in its layered, metamaterial-like structure. These results provide guidance for designing advanced EMI shielding materials but also highlight the need for exploring fundamental mechanisms behind interaction of electromagnetic waves with 2D materials.

https://science.sciencemag.org/content/sci/369/6502/446.full.pdf

Anomalous absorption of electromagnetic waves by 2D transition metal carbonitride Ti3CNTx (MXene)

Miniaturization of electronics demands electromagnetic interference (EMI) shielding of nanoscale dimension. The authors report a systematic exploration of EMI shielding behavior of 2D Ti3 C2 Tx MXene assembled films over a broad range of film thicknesses, monolayer by monolayer. Theoretical models are used to explain the shielding mechanism below skin depth, where multiple reflection becomes significant, along with the surface reflection and bulk absorption of electromagnetic radiation. While a monolayer assembled film offers ≈20% shielding of electromagnetic waves, a 24-layer film of ≈55 nm thickness demonstrates 99% shielding (20 dB), revealing an extraordinarily large absolute shielding effectiveness (3.89 × 106 dB cm2 g-1 ). This remarkable performance of nanometer-thin solution processable MXene proposes a paradigm shift in shielding of lightweight, portable, and compact next-generation electronic devices.

Electromagnetic Shielding of Monolayer MXene Assemblies.

With the widespread application of electronic communication technology, the resulting electromagnetic radiation pollution has been significantly increased. Metal matrix electromagnetic interference (EMI) shielding materials have disadvantages such as high density, easy corrosion, difficult processing and high price, etc. Polymer matrix EMI shielding composites possess light weight, corrosion resistance and easy processing. However, the current polymer matrix composites present relatively low electrical conductivity and poor EMI shielding performance. This review firstly discusses the key concept, loss mechanism and test method of EMI shielding. Then the current development status of EMI shielding materials is summarized, and the research progress of polymer matrix EMI shielding composites with different structures is illustrated, especially for their preparation methods and evaluation. Finally, the corresponding key scientific and technical problems are proposed, and their development trend is also prospected.

/pdf/structural-design-strategies-of-polymer-matrix-composites-4o090gtk1u.pdf

Structural Design Strategies of Polymer Matrix Composites for Electromagnetic Interference Shielding: A Review.

Multi-junction (tandem) solar cells (TSCs) consisting of multiple light absorbers with considerably different band gaps show great potential in breaking the Shockley–Queisser (S–Q) efficiency limit of a single junction solar cell by absorbing light in a broader range of wavelengths. Perovskite solar cells (PSCs) are ideal candidates for TSCs due to their tunable band gaps, high PCE up to 25.2%, and easy fabrication. PSCs with high PCEs are typically fabricated via a low temperature solution method, which are easy to combine with many other types of solar cells like silicon (Si), copper indium gallium selenide (CIGS), narrow band gap PSCs, dye-sensitized, organic, and quantum dot solar cells. As a matter of fact, perovskite TSCs have stimulated enormous scientific and industrial interest since their first development in 2014. Significant progress has been made on the development of perovskite TSCs both in the research laboratories and industrial companies. This review will rationalize the recent exciting advancement in perovskite TSCs. We begin with the introduction of the historical development of TSCs in a broader context, followed by the summary of the state-of-the-art development of perovskite TSCs with various types of device architectures. We then discuss the strategies for improving the PCEs of perovskite TSCs, including but not limited to the design considerations on the transparency of perovskite absorbers and metal electrodes, protective layers, and recombination layers (RLs)/tunnel junctions (TJs), with a particular focus on the band gap tuning and thickness adjustment of active layers. We subsequently introduce a range of measurement techniques for the characterization of perovskite TSCs. We also cover other core issues related to the large-scale applications and commercialization. Finally, we offer our perspectives on the future development of emerging photovoltaic technologies as the device performance enhancement and cost reduction are central to almost any type of solar cell applied in the perovskite TSCs.

Perovskite Tandem Solar Cells: From Fundamentals to Commercial Deployment

Exploring an electromagnetic interference (EMI) shielding material with lightweight, flexible and easy fabricating process to deal with the increasingly serious electromagnetic environment pollution has become a current developing trend. Here, we reported a novel cellulose nanofiber (CNF)/silver nanowire (AgNW) conductive paper with a distinctive hierarchical structure by a facile “blending-filtration-peeling” process. Results showed that the obtained paper with a thickness of ~40 μm exhibited excellent tensile strength of ~49.1 MPa, a low percolation threshold of 1.4 vol% AgNWs, no significant changes in electrical conductivity after 2000 bending. The outstanding synergy between green CNFs and AgNWs endowed the paper with high EMI shielding effectiveness of up to 39.3 dB in X band and effective shielding effects on electromagnetic signals for realistic mobile phone communication. The special CNF/AgNW papers are expected to broaden new application fields as electronic devices e.g. flexible electronic components or effective ultra-thin EMI shielding materials for daily demands.

Ultra-thin and highly flexible cellulose nanofiber/silver nanowire conductive paper for effective electromagnetic interference shielding

A kind of pollution known as electromagnetic interference (EMI), which results from ubiquitous usage of various electronic communication and military radar equipment, has been receiving increasing attention recently. However, large-area EMI shielding on transparent and/or curved surfaces, including building windows, curved glass wall, and special requirements spaces (SRSs), remains hard to achieve. In this paper, a silver nanofiber (AgNF) based flexible and transparent EMI shielding film was successfully assembled via a room-temperature roll-to-roll production method. For transparent application scenario, AgNF with 89% transmittance in visible range and 1 μm thickness shows ~20 dB shielding efficiency (EMI SE). On the other hand, total shielding (>50 dB) is obtained when the thickness of AgNF increases to 10 μm, while its transmittance in visible range remains higher than 75%. Considering the facile and scale-free production technology, this material can be readily applied in large-scale, transparent, and/or SRSs EMI shielding.

/pdf/room-temperature-production-of-silver-nanofiber-film-for-12a5gr23ce.pdf

Room-temperature production of silver-nanofiber film for large-area, transparent and flexible surface electromagnetic interference shielding

Manufacturing a flexible, light, large-area, and high-efficiency electromagnetic shielding materials in a straightforward and cost-effective manner presently remains a significant challenge. In this work, we propose a conductive network design and verify its electromagnetic interference (EMI) shielding effectiveness (SE) by simulation. Using the structure and parameters obtained by simulation, we prepare a flexible EMI shielding material using silver nanowires (AgNWs)/polyvinyl butyral (PVB) ethanol solution and textile substructure via a facile immersing method. In the frequency range of 5–18 GHz, the AgNWs/PVB textile with 1.4 mm thickness achieves an EMI SE of 59 dB, which exceeds the requirements for commercial applications. Due to the low density of 56 mg/cm3, specific shielding effectiveness (SSE) of this material reaches 1053 dB m3/g. It is found that the AgNWs/PVB textile is more resistant to washing with water and oxidation than AgNWs textile without a PVB protector. As a result, the conductivity of AgNWs/PVB textile exhibits no change after washing with water and varies slightly after being kept in hot air. We find that a signal monitor is unable to detect a signal emitted by a mobile phone from a jacket lined with AgNWs/PVB textile. AgNWs/PVB textile with these properties can be mass-produced as high-efficiency EMI shielding material for commercial applications.

/pdf/a-large-area-agnw-modified-textile-with-high-performance-1qnrstggfs.pdf

Qingmin Wang

Papers

Room-temperature production of silver-nanofiber film for large-area, transparent and flexible surface electromagnetic interference shielding

A large-area AgNW-modified textile with high-performance electromagnetic interference shielding

Highly Robust, Flexible, and Large-Scale 3D-Metallized Sponge for High-Performance Electromagnetic Interference Shielding