Ultrafast Delamination of Graphite into High-Quality Graphene Using Alternating Currents

To bridge the gap between laboratory‐scale studies and commercial applications, mass production of high quality graphene is essential. A scalable exfoliation strategy towards the production of graphene sheets is presented that has excellent yield (ca. 75 %, 1–3 layers), low defect density (a C/O ratio of 21.2), great solution‐processability, and outstanding electronic properties (a hole mobility of 430 cm2 V−1 s−1). By applying alternating currents, dual exfoliation at both graphite electrodes enables a high production rate exceeding 20 g h−1 in laboratory tests. As a cathode material for lithium storage, graphene‐wrapped LiFePO4 particles deliver a high capacity of 167 mAh g−1 at 1 C rate after 500 cycles

An open-access database and analysis tool for perovskite solar cells based on the FAIR data principles

Large datasets are now ubiquitous as technology enables higher-throughput experiments, but rarely can a research field truly benefit from the research data generated due to inconsistent formatting, undocumented storage or improper dissemination. Here we extract all the meaningful device data from peer-reviewed papers on metal-halide perovskite solar cells published so far and make them available in a database. We collect data from over 42,400 photovoltaic devices with up to 100 parameters per device. We then develop open-source and accessible procedures to analyse the data, providing examples of insights that can be gleaned from the analysis of a large dataset. The database, graphics and analysis tools are made available to the community and will continue to evolve as an open-source initiative. This approach of extensively capturing the progress of an entire field, including sorting, interactive exploration and graphical representation of the data, will be applicable to many fields in materials science, engineering and biosciences

Two-Dimensional Violet Phosphorus: A p-Type Semiconductor for (Opto)electronics

International audienceThe synthesis of novel two-dimensional (2D) materials displaying an unprecedented composition and structure via the exfoliation of layered systems provides access to uncharted properties. For application in optoelectronics, a vast majority of exfoliated 2D semiconductors possess n-type or more seldom ambipolar characteristics. The shortage of p-type 2D semiconductors enormously hinders the extensive engineering of 2D devices for complementary metal oxide semiconductors (CMOSs) and beyond CMOS applications. However, despite the recent progress in the development of 2D materials endowed with p-type behaviors by direct synthesis or p-doping strategies, finding new structures is still of primary importance. Here, we report the sonication-assisted liquid-phase exfoliation of violet phosphorus (VP) crystals into few-layer-thick flakes and the first exploration of their electrical and optical properties. Field-effect transistors based on exfoliated VP thin films exhibit a p-type transport feature with an Ion/Ioff ratio of 10^4 and a hole mobility of 2.25 cm2 V–1 s–1 at room temperature. In addition, the VP film-based photodetectors display a photoresponsivity (R) of 10 mA W–1 and a response time down to 0.16 s. Finally, VP embedded into CMOS inverter arrays displays a voltage gain of ∼17. This scalable production method and high quality of the exfoliated material combined with the excellent optoelectronic performances make VP an enticing and versatile p-type candidate for next-generation more-than-Moore (opto)electronics

Solution-Processable High-Quality Graphene for Organic Solar Cells

The unique optical and electronic properties of graphene open up new opportunities for optoelectronics. This work reports the use of <i>solution-processed</i> high-quality graphene as transparent conductive electrode in an organic solar cell using an electrochemical approach. The fabricated thieno­[3,4-<i>b</i>]­thiophene/benzo­dithiophene:phenyl-C₇₁-butyric acid methyl ester (PTB7:PCB₇₁M) bulk heterojunction organic solar cell based on the exfoliated graphene (EG) anode exhibits a power conversion efficiency of 4.23%, making EG promising for next-generation flexible optoelectronic devices

Tuning the Piezoresistive Behavior of Graphene-Polybenzoxazine Nanocomposites: Toward High-Performance Materials for Pressure Sensing Applications

Flexible piezoresistive pressure sensors are key components in wearable technologies for health monitoring, digital healthcare, human–machine interfaces, and robotics. Among active materials for pressure sensing, graphene-based materials are extremely promising because of their outstanding physical characteristics. Currently, a key challenge in pressure sensing is the sensitivity enhancement through the fine tuning of the active material’s electro-mechanical properties. Here, we describe a novel versatile approach to modulating the sensitivity of graphene-based piezoresistive pressure sensors by combining chemically reduced graphene oxide (rGO) with a thermally responsive material, namely, a novel trifunctional polybenzoxazine thermoset precursor based on tris(3-aminopropyl)amine and phenol reagents (PtPA). The integration of rGO in a polybenzoxazine thermoresist matrix results in an electrically conductive nanocomposite where the thermally triggered resist’s polymerization modulates the active material rigidity and consequently the piezoresistive response to pressure. Pressure sensors comprising the rGO-PtPA blend exhibit sensitivities ranging from 10–2 to 1 kPa–1, which can be modulated by controlling the rGO:PtPA ratio or the curing temperature. Our rGO-PtPA blend represents a proof-of-concept graphene-based nanocomposite with on-demand piezoresistive behavior. Combined with solution processability and a thermal curing process compatible with large-area coatings technologies on flexible supports, this method holds great potential for applications in pressure sensing for health monitoring

CCDC 1435119: Experimental Crystal Structure Determination

Related Article: Ashok Keerthi, Cunbin An, Mengmeng Li, Tomasz Marszalek, Antonio Gaetano Ricciardulli, Boya Radha, Fares D. Alsewailem, Klaus Müllen, Martin Baumgarten|2016|Polym.Chem.|7|1545|doi:10.1039/C6PY00023

Embedded Nickel‐Mesh Transparent Electrodes for Highly Efficient and Mechanically Stable Flexible Perovskite Photovoltaics: Toward a Portable Mobile Energy Source

The rapid development of Internet of Things mobile terminals has accelerated the market's demand for portable mobile power supplies and flexible wearable devices. Here, an embedded metal‐mesh transparent conductive electrode (TCE) is prepared on poly(ethylene terephthalate) (PET) using a novel selective electrodeposition process combined with inverted film‐processing methods. This embedded nickel (Ni)‐mesh flexible TCE shows excellent photoelectric performance (sheet resistance of ≈0.2–0.5 Ω sq−1 at high transmittance of ≈85–87%) and mechanical durability. The PET/Ni‐mesh/polymer poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS PH1000) hybrid electrode is used as a transparent electrode for perovskite solar cells (PSCs), which exhibit excellent electric properties and remarkable environmental and mechanical stability. A power conversion efficiency of 17.3% is obtained, which is the highest efficiency for a PSC based on flexible transparent metal electrodes to date. For perovskite crystals that require harsh growth conditions, their mechanical stability and environmental stability on flexible transparent embedded metal substrates are studied and improved. The resulting flexible device retains 76% of the original efficiency after 2000 bending cycles. The results of this work provide a step improvement in flexible PSCs

Donor–Acceptor Conjugated Polymers for Single-Component Near-Infrared II Organic Phototransistors with Ultrahigh Photoresponsivity

The design of donor–acceptor (D–A) conjugated polymers with narrow bandgaps remains a big challenge for achieving high-performance near-infrared (NIR) phototransistors. Herein, we report a novel D–A conjugated polymer (denoted as TBOPV-DT) based on a thiophene-fused benzodifurandione-based oligo(p-phenylenevinylene) (TBOPV) acceptor in conjugation with a 3,3′-dialkoxy-2,2′-dithiophene (DT) donor. Benefiting from the alkoxylation of the donor units, the TBOPV-DT conjugated polymer exhibits broad second NIR absorption and a narrow bandgap of 0.65 eV. When being used as the channel material in field-effect transistors, the TBOPV-DT conjugated polymer shows p-type semiconducting behavior with a hole mobility of 0.16 cm2 V–1 s–1. Besides, the resulting single-component polymer phototransistor displays ultrahigh sensitivity to a broad range of wavelengths (850–1450 nm) and a record-high photoresponsivity of 1.9 × 105 A W–1. Moreover, the fast rise and decay response times of 53 and 317 ms, respectively, are comparable to those of state-of-the-art two-dimensional materials. This work sheds light on designing new narrow-bandgap D–A conjugated polymers with molecular precision and paves the way for the development of future high-performance optoelectronics