Showing papers on "Ternary operation published in 2017"

Reducing the efficiency–stability–cost gap of organic photovoltaics with highly efficient and stable small molecule acceptor ternary solar cells

Abstract: Technological deployment of organic photovoltaic modules requires improvements in device light-conversion efficiency and stability while keeping material costs low. Here we demonstrate highly efficient and stable solar cells using a ternary approach, wherein two non-fullerene acceptors are combined with both a scalable and affordable donor polymer, poly(3-hexylthiophene) (P3HT), and a high-efficiency, low-bandgap polymer in a single-layer bulk-heterojunction device. The addition of a strongly absorbing small molecule acceptor into a P3HT-based non-fullerene blend increases the device efficiency up to 7.7 ± 0.1% without any solvent additives. The improvement is assigned to changes in microstructure that reduce charge recombination and increase the photovoltage, and to improved light harvesting across the visible region. The stability of P3HT-based devices in ambient conditions is also significantly improved relative to polymer:fullerene devices. Combined with a low-bandgap donor polymer (PBDTTT-EFT, also known as PCE10), the two mixed acceptors also lead to solar cells with 11.0 ± 0.4% efficiency and a high open-circuit voltage of 1.03 ± 0.01 V. Ternary organic blends using two non-fullerene acceptors are shown to improve the efficiency and stability of low-cost solar cells based on P3HT and of high-performance photovoltaic devices based on low-bandgap donor polymers.

Ternary NiCo 2 P x Nanowires as pH-Universal Electrocatalysts for Highly Efficient Hydrogen Evolution Reaction.

Abstract: A bimetallic-structured ternary phosphide (NiCo2 Px ) as a novel pH-universal electrocatalyst for hydrogen evolution reaction is presented. It exhibits both high activity and long-term stability in all the tested alkaline, neutral, and acidic media. The excellent catalytic performance endows it with a bright future in the large-scale electrochemical water splitting industry.

High-Performance Ternary Organic Solar Cell Enabled by a Thick Active Layer Containing a Liquid Crystalline Small Molecule Donor.

Abstract: Ternary organic solar cells (OSCs) have attracted much research attention in the past few years, as ternary organic blends can broaden the absorption range of OSCs without the use of complicated tandem cell structures. Despite their broadened absorption range, the light harvesting capability of ternary OSCs is still limited because most ternary OSCs use thin active layers of about 100 nm in thickness, which is not sufficient to absorb all photons in their spectral range and may also cause problems for future roll-to-roll mass production that requires thick active layers. In this paper, we report a highly efficient ternary OSC (11.40%) obtained by incorporating a nematic liquid crystalline small molecule (named benzodithiophene terthiophene rhodanine (BTR)) into a state-of-the-art PTB7-Th:PC71BM binary system. The addition of BTR into PTB7-Th:PC71BM was found to improve the morphology of the blend film with decreased π–π stacking distance, enlarged coherence length, and enhanced domain purity. This resulte...

Ternary Polymer Solar Cells based on Two Acceptors and One Donor for Achieving 12.2% Efficiency.

Abstract: Ternary polymer solar cells are fabricated based on one donor PBDB-T and two acceptors (a methyl-modified small-molecular acceptor (IT-M) and a bis-adduct of Bis[70]PCBM). A high power conversion efficiency of 12.2% can be achieved. The photovoltaic performance of the ternary polymer solar cells is not sensitive to the composition of the blend.

Facile synthesis of yolk–shell Ni@void@SnO2(Ni3Sn2) ternary composites via galvanic replacement/Kirkendall effect and their enhanced microwave absorption properties

Abstract: Yolk–shell ternary composites composed of a Ni sphere core and a SnO2(Ni3Sn2) shell were successfully prepared by a facile two-step method. The size, morphology, microstructure, and phase purity of the resulting composites were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, transmission electron microscopy (TEM), high-resolution TEM, selected-area electron diffraction, and powder X-ray diffraction. The core sizes, interstitial void volumes, and constituents of the yolk–shell structures varied by varying the reaction time. A mechanism based on the time-dependent experiments was proposed for the formation of the yolk–shell structures. The yolk–shell structures were formed by a synergistic combination of an etching reaction, a galvanic replacement reaction, and the Kirkendall effect. The yolk–shell ternary SnO2 (Ni3Sn2)@Ni composites synthesized at a reaction time of 15 h showed excellent microwave absorption properties. The reflection loss was found to be as low as–43 dB at 6.1 GHz. The enhanced microwave absorption properties may be attributed to the good impedance match, multiple reflections, the scattering owing to the voids between the core and the shell, and the effective complementarities between the dielectric loss and the magnetic loss. Thus, the yolk–shell ternary composites are expected to be promising candidates for microwave absorption applications, lithium ion batteries, and photocatalysis.

Ternary solar cells with a mixed face-on and edge-on orientation enable an unprecedented efficiency of 12.1%

Abstract: Ternary organic solar cells (OSCs), with a simple structure, can be easily adopted as sub-cells in a tandem design, thereby further enhancing the power conversion efficiency (PCE). Considering the potential to surpass the theoretical PCE limit in OSCs, we incorporated a benzo[1,2-b;4,5-b′]dithiophene-based small molecule into a poly(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b;4,5-b′]dithiophene-2,6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene-)-2-carboxylate-2-6-diyl):[6,6]-phenyl-C71-butyric acid methyl ester host system. A hitherto unrealized PCE of 12.1% was achieved at the optimized composition of the ternary blend. The ternary blend surprisingly had a face-on and edge-on co-existent texture, which is far better than that of the face-on orientated host film. To the best of our knowledge, this intriguing result refutes for the first time a general paradigm that high-performance OSCs are unambiguously linked to face-on structures. Therefore, our study provides a new platform for refining the theoretical underpinning of multiple blending OSCs.

Tuning Electronic Structures of Nonprecious Ternary Alloys Encapsulated in Graphene Layers for Optimizing Overall Water Splitting Activity

Abstract: Electrochemical water splitting is considered as the most promising technology for hydrogen production. Considering overall water splitting for practical applications, catalysis of the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) should be performed in the same electrolyte, especially in alkaline solutions. However, designing and searching for highly active and inexpensive electrocatalysts for both OER and HER in basic media remain significant challenges. Herein, we report a facile and universal strategy for synthesizing nonprecious transition metals, binary alloys, and ternary alloys encapsulated in graphene layers by direct annealing of metal–organic frameworks. Density functional theory calculations prove that with an increase in the degree of freedom of alloys or a change in the metal proportions in FeCoNi ternary alloys, the electronic structures of materials can also be tuned intentionally by changing the number of transferred electrons between alloys and graphene. The optim...

Ternary Porous Cobalt Phosphoselenide Nanosheets: An Efficient Electrocatalyst for Electrocatalytic and Photoelectrochemical Water Splitting.

Abstract: Exploring efficient and earth-abundant electrocatalysts is of great importance for electrocatalytic and photoelectrochemical hydrogen production. This study demonstrates a novel ternary electrocatalyst of porous cobalt phosphoselenide nanosheets prepared by a combined hydrogenation and phosphation strategy. Benefiting from the enhanced electric conductivity and large surface area, the ternary nanosheets supported on electrochemically exfoliated graphene electrodes exhibit excellent catalytic activity and durability toward hydrogen evolution in alkali, achieving current densities of 10 and 20 mA cm−2 at overpotentials of 150 and 180 mV, respectively, outperforming those reported for transition metal dichalcogenides and first-row transition metal pyrites catalysts. Theoretical calculations reveal that the synergistic effects of Se vacancies and subsequent P displacements of Se atoms around the vacancies in the resulting cobalt phosphoselenide favorably change the electronic structure of cobalt selenide, assuring a rapid charge transfer and optimal energy barrier of hydrogen desorption, and thus promoting the proton kinetics. The overall-water-splitting with 10 mA cm−2 at a low voltage of 1.64 V is achieved using the ternary electrode as both the anode and cathode, and the performance surpasses that of the Ir/C–Pt/C couple for sufficiently high overpotentials. Moreover, the integration of ternary nanosheets with macroporous silicon enables highly efficient solar-driven photoelectrochemical hydrogen production.

Highly Efficient Ternary‐Blend Polymer Solar Cells Enabled by a Nonfullerene Acceptor and Two Polymer Donors with a Broad Composition Tolerance

Abstract: In this work, highly efficient ternary-blend organic solar cells (TB-OSCs) are reported based on a low-bandgap copolymer of PTB7-Th, a medium-bandgap copolymer of PBDB-T, and a wide-bandgap small molecule of SFBRCN. The ternary-blend layer exhibits a good complementary absorption in the range of 300–800 nm, in which PTB7-Th and PBDB-T have excellent miscibility with each other and a desirable phase separation with SFBRCN. In such devices, there exist multiple energy transfer pathways from PBDB-T to PTB7-Th, and from SFBRCN to the above two polymer donors. The hole-back transfer from PTB7-Th to PBDB-T and multiple electron transfers between the acceptor and the donor materials are also observed for elevating the whole device performance. After systematically optimizing the weight ratio of PBDB-T:PTB7-Th:SFBRCN, a champion power conversion efficiency (PCE) of 12.27% is finally achieved with an open-circuit voltage (Voc) of 0.93 V, a short-circuit current density (Jsc) of 17.86 mA cm−2, and a fill factor of 73.9%, which is the highest value for the ternary OSCs reported so far. Importantly, the TB-OSCs exhibit a broad composition tolerance with a high PCE over 10% throughout the whole blend ratios.

Layered ternary M(n+1)AX(n) phases and their 2D derivative MXene: an overview from a thin-film perspective

Abstract: Inherently and artificially layered materials are commonly investigated both for fundamental scientific purposes and for technological application. When a layered material is thinned or delaminated ...

9.0% power conversion efficiency from ternary all-polymer solar cells

Abstract: Integration of a third component into a single-junction polymer solar cell (PSC) is regarded as an attractive strategy to enhance the performance of PSCs. Although binary all-polymer solar cells (all-PSCs) have recently emerged with compelling power conversion efficiencies (PCEs), the PCEs of ternary all-PSCs still lag behind those of the state-of-the-art binary all-PSCs, and the advantages of ternary systems are not fully exploited. In this work, we realize high-performance ternary all-PSCs with record-breaking PCEs of 9% and high fill factors (FF) of over 0.7 for both conventional and inverted devices. The improved photovoltaic performance benefits from the synergistic effects of extended absorption, more efficient charge generation, optimal polymer orientations and suppressed recombination losses compared to the binary all-PSCs, as evidenced by a set of experimental techniques. The results provide new insights for developing high-performance ternary all-PSCs by choosing appropriate donor and acceptor polymers to overcome limitations in absorption, by affording good miscibility, and by benefiting from charge and energy transfer mechanisms for efficient charge generation.

High-performance ternary organic solar cells with thick active layer exceeding 11% efficiency

Abstract: We present a novel ternary organic solar cell with an uncommonly thick active layer (∼300 nm), featuring thickness invariant charge carrier recombination and delivering 11% power conversion efficiency (PCE). A ternary blend was used to demonstrate photovoltaic modules of high technological relevance both on glass and flexible substrates, yielding 8.2% and 6.8% PCE, respectively.

Room temperature hydrogen gas sensor based on palladium decorated tin oxide/molybdenum disulfide ternary hybrid via hydrothermal route

Abstract: This paper demonstrates a hydrogen gas sensor based on palladium-tin oxide- molybdenum disulfide (Pd-SnO 2 /MoS 2 ) ternary hybrid via hydrothermal route. The morphologies, microstructures and compositional characteristics of the Pd-SnO 2 /MoS 2 nanocomposite were sufficiently examined by X-ray diffraction (XRD), Raman spectroscopy (RS), nitrogen sorption analysis, energy dispersive spectrometer (EDS), scanning electron microscopy (SEM), transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS). The gas-sensing performances of the Pd-SnO 2 /MoS 2 sensor were investigated by exposed to different concentrations of hydrogen gas from 30 ppm to 5000 ppm at room temperature. The experimental results showed that the hydrogen gas sensor has a quite sensitive response, swift response-recovery time, good repeatability and selectivity toward hydrogen gas. Furthermore, the effect of Pd loading in the hybrid on the hydrogen gas sensing was investigated. The sensing mechanism of the Pd-SnO 2 /MoS 2 sensor was attributed to the synergistic effect of the ternary nanostructures and the modulation of potential barrier with electron transfer. This work indicates that the as-prepared Pd-SnO 2 /MoS 2 composite is a candidate for detecting hydrogen gas in various applications at room temperature.

Achieving High‐Performance Ternary Organic Solar Cells through Tuning Acceptor Alloy

Abstract: Acceptor alloys based on n-type small molecular and fullerene derivatives are used to fabricate the ternary solar cell. The highest performance of optimized ternary device is 10.4%, which is the highest efficiency for one donor/two acceptors-based ternary systems. Three important parameters, JSC , VOC , and FF, of the optimized ternary device are all higher than the binary reference devices.

Nematic liquid crystal materials as a morphology regulator for ternary small molecule solar cells with power conversion efficiency exceeding 10

Abstract: Solution-processed small molecule solar cells (SMSCs) are fabricated based on DRCN5T:PC71BM as active layers, the power conversion efficiency (PCE) is markedly increased from 3.63% to 9.11% for the active layers undergoing up-side-down thermal annealing and solvent vapor annealing post-treatments. The PCE improvement should be attributed to the appropriate phase separation consisting of enhanced crystallinity of donor and purified acceptor domain at nanoscale. The nematic liquid crystal small molecule BTR is selected as the second donor and morphology regulator to prepare ternary SMSCs. The champion PCE of ternary SMSCs was improved to 10.05% by mixing 1.5 wt% BTR, which corresponds to a 10.3% PCE improvement compared with the optimized binary SMSCs. The performance improvement is mainly attributed to the further optimized phase separation and complementary photon harvesting between DRCN5T and BTR, which could be well demonstrated from absorption spectra, two dimensional grazing incidence X-ray diffraction (2D-GIXD) and transmission electron microscopy (TEM).

Facile Synthesis of Three-Dimensional Ternary ZnCo2O4/Reduced Graphene Oxide/NiO Composite Film on Nickel Foam for Next Generation Supercapacitor Electrodes

Abstract: Ternary ZnCo2O4/reduced graphene oxide/NiO (ZCGNO) nanowire arrays were grown directly on a piece of Ni foam using a simple, facile, cost-effective hydrothermally assisted thermal annealing process without the addition of any Ni precursor salt and used as a binder-free supercapacitor electrode. Ni foam was utilized successively as the NiO precursor, binder, and current collector. The resulting 3D ternary composite possessed an ultrahigh specific capacitance of 1256 F/g at a current density of 3 A/g in 6 M KOH solution. Moreover, the three-dimensional electrode exhibited superior electrochemical performance, such as excellent cyclic stability (∼80% capacitance retention after 3000 cycles), maximum energy density of 62.8 Wh/kg, maximum power density of 7492.5 W/kg, and low equivalent series resistance (0.58 Ω). The effects of the electrolyte concentration on the electrochemical performance of ZCGNO were also examined. ZCGNO with this remarkable electrochemical performance may be considered a prospective can...

Carbon Dioxide Electroreduction into Syngas Boosted by a Partially Delocalized Charge in Molybdenum Sulfide Selenide Alloy Monolayers.

Abstract: Structural parameters of ternary transition-metal dichalcogenide (TMD) alloy usually obey Vegard law well, while interestingly it often exhibits boosted electrocatalytic performances relative to its two pristine binary TMDs. To unveil the underlying reasons, we propose an ideal model of ternary TMDs alloy monolayer. As a prototype, MoSeS alloy monolayers are successfully synthesized, in which X-ray absorption fine structure spectroscopy manifests their shortened Mo-S and lengthened Mo-Se bonds, helping to tailor the d-band electronic structure of Mo atoms. Density functional theory calculations illustrate an increased density of states near their conduction band edge, which ensures faster electron transfer confirmed by their lower work function and smaller charge-transfer resistance. Energy calculations show the off-center charge around Mo atoms not only benefits for stabilizing COOH* intermediate confirmed by its most negative formation energy, but also facilitates the rate-limiting CO desorption step verified by CO temperature programmed desorption and electro-stripping tests. As a result, MoSeS alloy monolayers attain the highest 45.2 % Faradaic efficiency for CO production, much larger than that of MoS2 monolayers (16.6 %) and MoSe2 monolayers (30.5 %) at -1.15 V vs. RHE. This work discloses how the partially delocalized charge in ternary TMDs alloys accelerates electrocatalytic performances at atomic level, opening new horizons for manipulating CO2 electroreduction properties.

Two Well‐Miscible Acceptors Work as One for Efficient Fullerene‐Free Organic Solar Cells

Abstract: High-performance ternary organic solar cells are fabricated by using a wide-bandgap polymer donor (bithienyl-benzodithiophene-alt-fluorobenzotriazole copolymer, J52) and two well-miscible nonfullerene acceptors, methyl-modified nonfullerene acceptor (IT-M) and 2,2'-((2Z,2'Z)-((5,5'-(4,4,9,9-tetrakis(4-hexylphenyl)-4,9-dihydros-indaceno[1,2-b:5,6-b']dithiophene-2,7-diyl)bis(4-((2-ethylhexyl)oxy)thiophene-5,2-diyl))bis(methanylylidene))bis(3-oxo-2,3-dihydro-1H-indene-2,1-diylidene))dimalononitrile (IEICO). The two acceptors with complementary absorption spectra and similar lowest unoccupied molecular orbital levels show excellent compatibility in the blend due to their very similar chemical structures. Consequently, the obtained ternary organic solar cells (OSC) exhibits a high efficiency of 11.1%, with an enhanced short-circuit current density of 19.7 mA cm-2 and a fill factor of 0.668. In this ternary system, broadened absorption, similar output voltages, and compatible morphology are achieved simultaneously, demonstrating a promising strategy to further improve the performance of ternary OSCs.

Direct growth of ternary Ni–Fe–P porous nanorods onto nickel foam as a highly active, robust bi-functional electrocatalyst for overall water splitting

Abstract: To date, metal organic frameworks (MOFs) have emerged as a new platform to endow electrocatalysts with multi-scale architectures. Herein, we report a universal MOF-based post-treatment strategy to produce carbon-incorporated ternary Ni–Fe–P porous nanorods grown onto nickel foam directly as a non-precious-metal bifunctional electrocatalyst.

Inhibiting grain coarsening and inducing oxygen vacancies: the roles of Mn in achieving a highly reversible conversion reaction and a long life SnO2–Mn–graphite ternary anode

Abstract: To obtain highly reversible conversion reactions, high Coulombic efficiencies, and long lifetimes in SnO2-based anodes for lithium storage, a new ternary SnO2–Mn–graphite composite has been constructed by scalable ball-milling. It is demonstrated that nanosized Mn additives successfully inhibit Sn coarsening, and favor the formation of oxygen vacancies in SnO2, which together promote the high reversibility of conversion reactions in lithiated SnO2. The SnO2–Mn binary hybrid with 30 wt% Mn contributes a stable long-life with a capacity retention of 100% after 900 cycles at 1 A g−1. The ternary SnO2–Mn–graphite composite demonstrates high average initial Coulombic efficiencies of ∼77%, large stable capacities of 850 mA h g−1 at 0.2 A g−1, and long lifetimes of more than 1000 cycles at both high rates (2 A g−1) and narrow potential ranges (0.01–2.4 V), with Coulombic efficiencies of 99.7%, which are among the best reported so far for SnO2-based anode materials. The simple material design strategy and fabrication method, together with the excellent electrochemical performances, demonstrate that this new ternary SnO2–Mn–graphite composite could contribute a new class of Sn-based anode materials for high capacity battery applications.

Highly Efficient Parallel-Like Ternary Organic Solar Cells

Abstract: Ternary bulk heterojunction (BHJ) blends have been demonstrated as a promising approach to increase the power conversion efficiencies (PCEs) of organic solar cells. Currently, most studies of ternary organic solar cells are based on blends of two donors and one acceptor, because of the limitation in acceptor materials. Here, we report that high-performance ternary solar cells have been fabricated with a wide-bandgap polymer donor (PDBT-T1) and two acceptor materials, phenyl-C70-butyric acid methyl ester (PC70BM), and nonfullerene acceptor (ITIC-Th). The addition of ITIC-Th into the BHJ blends dramatically increases the light absorption. Consequently, the champion ternary solar cell shows a high PCE of ∼10.5%, with an open-circuit voltage (Voc) of 0.95 V, a short-circuit current (Jsc) of 15.60 mA/cm2, and a fill factor (FF) of 71.1%, which largely outperforms their binary counterparts. Detailed studies reveal that the ternary solar cells work in a parallel-like device model (ITIC-Th and PC70BM form their o...

Facile Synthesis of MoS2/g-C3N4/GO Ternary Heterojunction with Enhanced Photocatalytic Activity for Water Splitting

Abstract: On the basis of a simple ion exchange method, a MoS2/g-C3N4/graphene oxide (GO) ternary nanojunction was constructed as an efficient photocatalyst for hydrogen evolution using solar energy. The confinement effect in MoS2 and g-C3N4 quantum dots enhances their water-splitting redox activities. The designed heterostructure featured a band alignment that facilitates the collection of electrons in MoS2 and holes in g-C3N4, effectively suppressing the recombination of photogenerated charge carriers. Furthermore, the GO with high specific surface area serves as an excellent conductive substrate to transport holes speedily. This study thus provides a novel and facile route of establishing efficient composite photocatalyst with multinary components for energy conversion.

Study of mixed ternary transition metal ferrites as potential electrodes for supercapacitor applications

Abstract: Nanocrystallites of three mixed ternary transition metal ferrite (MTTMF) were prepared by a facile sol–gel method and adopted as electrode material for supercapacitors. The phase development of the samples was determined using Fourier transform infrared (FT-IR) and thermal gravimetric analysis (TG). X-ray diffraction (XRD) analysis revealed the formation of a single-phase spinel ferrite in CuCoFe2O4 (CuCoF), NiCoFe2O4 (NiCoF) and NiCuFe2O4 (NiCuF). The surface characteristics and elemental composition of the nanocomposites have been studied by means of field emission scanning electron microscopy (FESEM), as well as energy dispersive spectroscopy (EDS). The electrochemical performance of the nanomaterials was evaluated using a two-electrode configuration by cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic technique in 1 M KOH electrolyte and was found to be in the order of: CuCoF > NiCoF > NiCuF. A maximum specific capacitance of 221 Fg−1 was obtained with CuCoF at a scan rate of 5 mV s−1. In addition to an excellent cycling stability, an energy density of 7.9 kW kg−1 was obtained at a current density of 1 Ag−1. The high electrochemical performance of the MTTMF nanocomposites obtained indicates that these materials are promising electrodes for supercapacitors.

Carbon nitride coupled with CdS-TiO2 nanodots as 2D/0D ternary composite with enhanced photocatalytic H2 evolution: A novel efficient three-level electron transfer process

Abstract: Photocatalytic H 2 evolution from water splitting requires an efficient photocatalyst with excellent charge separation ability and broad visible-light adsorption region. 0D CdS-TiO 2 nanodots (NDs) were successfully decorated on the 2D g-C 3 N 4 sheets via an epitaxial growth process. The as-synthesized ternary composite of CdS-TiO 2 @g-C 3 N 4 exhibits enhanced visible-light-driven photocatalytic H 2 evolution activity, as compared to the binary composites and their single components, which is about 6.7 and 11.2 times higher than those of single CdS and g-C 3 N 4 , respectively. Moreover, the as-obtained ternary composite has an external quantum efficiency (EQE) of 11.9% at 420 nm, implying the high utilization efficiency of photo-induced charges. In addition, the superior photostability can be achieved by this coupling method. The enhanced photocatalytic activity was attributed to the efficient charge separation originated from the three-level electron transfer system, the matched energy level positions, the abundant adsorption sites and active sites (0D/2D structure) and the synergistic effect among CdS, TiO 2 and g-C 3 N 4 . The work present here demonstrated that the construction of this three-level electron transfer system is an effective strategy to design more efficient ternary materials toward solar energy conversion (like H 2 production and CO 2 reduction).

Metal–Semiconductor Phase-Transition in WSe2(1-x)Te2x Monolayer

Abstract: A metal-semiconductor phase transition in a ternary transition metal dichalcogenide (TMD) monolayer is achieved by alloying Te into WSe2 (WSe2(1-x) Te2x , where x = 0%-100%). The optical bandgaps of the WSe2(1-x) Te2x monolayer can be tuned from 1.67 to 1.44 eV (2H semiconductor) and drops to 0 eV (1Td metal), which opens up an exciting opportunity in functional electronic/optoelectronic devices.

Recent advances in ternary two-dimensional materials: synthesis, properties and applications

Abstract: Two-dimensional (2D) materials have gained significant attention owing to their unique physical and chemical properties, which arise mainly from their high surface–bulk ratios and topological effects. Since the discovery of graphene in 2004, the family of 2D materials has expanded rapidly. Thus far, several single-element 2D materials (graphene, phosphorene, etc.) have been reported; the majority of them contain two (MoS2, WSe2, etc.) or more elements (Mo2CTx, CrPS4, Bi2Sr2CaCu2Ox, etc.). Of these, three-element 2D materials, also called ternary 2D materials, represent a rather attractive direction of recent years. Typical ternary 2D materials include metal phosphorous trichalcogenides (MPTs), ternary transition metal chalcogenides (TMDs), transition metal carbides and nitrides (MXenes) and 2D ternary oxides. Ternary 2D systems result in multiple degrees of freedom to tailor their physical properties via stoichiometric variation. Moreover, they exhibit some properties not characteristic of binary 2D systems, such as band gap tuning. In this paper, we have reviewed the recent progress in various ternary 2D materials on the basis of their classification (MPTs, ternary 2D MXenes, ternary TMDs, BCN and other ternary 2D materials). The synthesis methods, structures, key properties (such as band gap tuning, phase transition and topological phase), and their applications, are summarized. In addition, the strategies to tackle challenges, as well as the outlooks of this field, are presented.