Substrate‐Free and Shapeless Planar Micro‐Supercapacitors

2019-12-17T04:31:59+00:00December 17th, 2019|Categories: Publications|Tags: , |

Substrate‐free and shapeless planar micro‐supercapacitors are fabricated by encapsulating ultrathin microelectrodes made from 2D materials in different geometries with graphene‐oxide‐incorporated hydrogel electrolyte, showing high‐performance tenability and arbitrary form factors, in particular, unprecedented mechanical flexibility even under extreme crumpling, rolling, or spiral deformation while still maintaining the initial performance. Abstract Micro‐supercapacitors (MSCs), albeit powerful, are unable to broaden their potential applications primarily because they are not as flexible and morphable as electronics. To address this problem, a universal strategy to fabricate substrate‐free, ultrathin, shapeless planar‐MSCs with high‐performance tenability under serious deformation is put forward. These represent a new class of “all‐inside‐one” film supercapacitors, achieved by encapsulating two‐dimensional interdigital microelectrodes within chemically cross‐linked polyvinyl‐alcohol‐based hydrogel electrolyte containing graphene oxide (GO). GO nanosheets significantly improve ionic conductivity, enhance the capacitance, and boost robustness of hydrogel electrolyte. Consequently, the entire MSC, while being only 37 µm thick, can be crumpled and its shape can self‐adjust through fluid channel ten times smaller than its original size without any damage, demonstrating shapelessness. Using MXene as active material, high single‐cell areal capacitance of 40.8 mF cm−2 is achieved from microelectrodes as thin as 5 µm. Furthermore, to demonstrate wide applicability of this protocol, screen‐printed graphene‐based highly integrated MSCs connecting nine cells in series are fabricated to stably output a high voltage of 7.2 V while crumpling them from 0.11 to 0.01 cm−3, manifesting superior performance uniformity. This protocol allows the coexistence of high performance with incredible flexibility that may greatly diversify MSCs’ applications.

Published in: "Advanced Functional Materials".

Low Voltage and Ferroelectric 2D Electron Devices Using Lead‐Free BaxSr1‐xTiO3 and MoS2 Channel

2019-12-14T00:31:58+00:00December 13th, 2019|Categories: Publications|Tags: |

The lead‐free inorganic high‐k dielectric BaxSr1–xTiO3 oxides have been successfully introduced to support MoS2 channels in field effect transistors, targeting both extremely low voltage operation and ferroelectric nonvolatile memory function by simply adjusting the composition ratio of Ba and Sr. Abstract Coupling between non‐toxic lead‐free high‐k materials and 2D semiconductors is achieved to develop low voltage field effect transistors (FETs) and ferroelectric non‐volatile memory transistors as well. In fact, low voltage switching ferroelectric memory devices are extremely rare in 2D electronics. Now, both low voltage operation and ferroelectric memory function have been successfully demonstrated in 2D‐like thin MoS2 channel FET with lead‐free high‐k dielectric BaxSr1‐xTiO3 (BST) oxides. When the BST surface is coated with a 5.5‐nm‐ultrathin poly(methyl methacrylate) (PMMA)‐brush for improved roughness, the MoS2 FET with BST (x = 0.5) dielectric results in an extremely low voltage operation at 0.5 V. Moreover, the BST with an increased Ba composition (x = 0.8) induces quite good ferroelectric memory properties despite the existence of the ultrathin PMMA layer, well switching the MoS2 FET channel states in a non‐volatile manner with a ±3 V low voltage pulse. Since the employed high‐k dielectric and ferroelectric oxides are lead‐free in particular, the approaches for applying high‐k BST gate oxide for 2D MoS2 FET are not only novel but also practical towards future low voltage nanoelectronics and green technology.

Published in: "Advanced Functional Materials".

Low Voltage and Ferroelectric 2D Electron Devices Using Lead‐Free BaxSr1‐xTiO3 and MoS2 Channel

2019-12-13T22:32:47+00:00December 13th, 2019|Categories: Publications|Tags: |

The lead‐free inorganic high‐k dielectric BaxSr1–xTiO3 oxides have been successfully introduced to support MoS2 channels in field effect transistors, targeting both extremely low voltage operation and ferroelectric nonvolatile memory function by simply adjusting the composition ratio of Ba and Sr. Abstract Coupling between non‐toxic lead‐free high‐k materials and 2D semiconductors is achieved to develop low voltage field effect transistors (FETs) and ferroelectric non‐volatile memory transistors as well. In fact, low voltage switching ferroelectric memory devices are extremely rare in 2D electronics. Now, both low voltage operation and ferroelectric memory function have been successfully demonstrated in 2D‐like thin MoS2 channel FET with lead‐free high‐k dielectric BaxSr1‐xTiO3 (BST) oxides. When the BST surface is coated with a 5.5‐nm‐ultrathin poly(methyl methacrylate) (PMMA)‐brush for improved roughness, the MoS2 FET with BST (x = 0.5) dielectric results in an extremely low voltage operation at 0.5 V. Moreover, the BST with an increased Ba composition (x = 0.8) induces quite good ferroelectric memory properties despite the existence of the ultrathin PMMA layer, well switching the MoS2 FET channel states in a non‐volatile manner with a ±3 V low voltage pulse. Since the employed high‐k dielectric and ferroelectric oxides are lead‐free in particular, the approaches for applying high‐k BST gate oxide for 2D MoS2 FET are not only novel but also practical towards future low voltage nanoelectronics and green technology.

Published in: "Advanced Functional Materials".

Energy Transport by Radiation in Hyperbolic Material Comparable to Conduction

2019-12-12T02:32:09+00:00December 12th, 2019|Categories: Publications|Tags: , |

Energy transport by electromagnetic waves inside hyperbolic material boron nitride is investigated. A microscopic many‐body model is developed and shows that radiative heat transfer is in the same order of magnitude as phononic heat transfer. Experiments on total thermal transport provide the same conclusion, and radiative transfer accounts for a larger fraction of total energy transport at higher temperatures. Abstract Radiation as a heat transfer mode inside a bulk material is usually negligible in comparison to conduction. Here, the contribution of radiation to energy transport inside a hyperbolic material, hexagonal boron nitride (hBN), is investigated. With hyperbolic dispersion, i.e., opposite signs of dielectric components along principal directions, phonon polaritons contribute significantly to energy transport due to a much greater number of propagating modes compared to that in a normal material. A many‐body model is developed to account for radiative heat transfer in a material with a nonuniform temperature distribution. The total radiative heat transfer through hBN is found to be largely contributed by the high‐κ modes within the Reststrahlen bands, and is comparable to phonon conduction. Experimental measurements of temperature‐dependent thermal transport also show that radiative contribution to thermal transport is of the same order as that from phonons. Therefore, this work shows, for the first time, radiative heat transfer inside a material can be comparable to phonon conductive heat transfer.

Published in: "Advanced Functional Materials".

Kinetic‐Oriented Construction of MoS2 Synergistic Interface to Boost pH‐Universal Hydrogen Evolution

2019-12-12T02:32:05+00:00December 12th, 2019|Categories: Publications|Tags: , , |

The rational design of the interfacial electrocatalyst heterostructure MoS2 is guided by the kinetics investigation. By optimizing the electronic structure based on the simultaneous modulation of the 3d‐band‐offsets of Ni, Co, and Mo near the interface, superior pH‐universal hydrogen evolution performances are achieved, which opens up a new strategy in the design of highly efficient electrocatalysts. Abstract As a prerequisite for a sustainable energy economy in the future, designing earth‐abundant MoS2 catalysts with a comparable hydrogen evolution catalytic performance in both acidic and alkaline environments is still an urgent challenge. Decreasing the energy barriers could enhance the catalysts’ activity but is not often a strategy for doing so. Here, the first kinetic‐oriented design of the MoS2‐based heterostructure is presented for pH‐universal hydrogen evolution catalysis by optimizing the electronic structure based on the simultaneous modulation of the 3d‐band‐offsets of Ni, Co, and Mo near the interface. Benefiting from this desirable electronic structure, the obtained MoS2/CoNi2S4 catalyst achieves an ultralow overpotential of 78 and 81 mV at 10 mA cm−2, and turnover frequency as high as 2.7 and 1.7 s−1 at the overpotential of 200 mV in alkaline and acidic media, respectively. The MoS2/CoNi2S4 catalyst represents one of the best hydrogen evolution reaction performing ones among MoS2‐based catalysts reported to date in both alkaline and acidic environments, and equally important is the remarkable long‐term stability with negligible activity loss after maintaining at 10 mA cm−2 for 48 h in both acid and base. This work highlights the potential to deeply understand and

Published in: "Advanced Functional Materials".

Nanoscale Selective Passivation of Electrodes Contacting a 2D Semiconductor

2019-12-12T02:31:41+00:00December 12th, 2019|Categories: Publications|Tags: |

A simple method for passivating the electrodes in contact with 2D‐semiconducting material, MoS2, is presented. Applying the potential to an electrode in a phenol solution causes the polymerization of a nonconductive polymer, poly(phenylene oxide) (PPO), which blocks the electrode surface. Since the polymerization occurs in the potential window where MoS2 is electrochemically inactive, PPO deposition is area‐selective, limited to the electrode surface. Abstract 2D semiconducting materials have become the central component of various nanoelectronic devices and sensors. For sensors operating in liquid, it is crucial to efficiently block the electron transfer that occurs between the electrodes contacting the 2D material and the interfering redox species. This reduces current leakages and preserves a good signal‐to‐noise ratio. Here, a simple electrochemical method is presented for passivating the electrodes contacting a monolayer of MoS2, a representative of transition metal dichalcogenide semiconductors. The method is based on blocking the electrode surface by a thin and compact layer of electronically nonconductive poly(phenylene oxide), PPO, formed by electrochemical polymerization of phenol. Since the phenol polymerization occurs in the potential window where MoS2 is electrochemically inactive, the PPO deposition is area‐selective, limited to the electrode surface. The deposited PPO film is characterized by electrochemical, X‐ray photoelectron spectroscopy, scanning electron microscopy, and atomic force microscopy techniques. The applicability of this method is demonstrated by coating the electrodes of a MoS2‐based field‐effect transistor coupled with a nanopore. The highly selective deposition, the simple approach, and the compatibility with MoS2 makes this method a good strategy for efficient insulation of

Published in: "Advanced Functional Materials".

Nanoscale Selective Passivation of Electrodes Contacting a 2D Semiconductor

2019-12-11T22:31:56+00:00December 11th, 2019|Categories: Publications|Tags: |

A simple method for passivating the electrodes in contact with 2D‐semiconducting material, MoS2, is presented. Applying the potential to an electrode in a phenol solution causes the polymerization of a nonconductive polymer, poly(phenylene oxide) (PPO), which blocks the electrode surface. Since the polymerization occurs in the potential window where MoS2 is electrochemically inactive, PPO deposition is area‐selective, limited to the electrode surface. Abstract 2D semiconducting materials have become the central component of various nanoelectronic devices and sensors. For sensors operating in liquid, it is crucial to efficiently block the electron transfer that occurs between the electrodes contacting the 2D material and the interfering redox species. This reduces current leakages and preserves a good signal‐to‐noise ratio. Here, a simple electrochemical method is presented for passivating the electrodes contacting a monolayer of MoS2, a representative of transition metal dichalcogenide semiconductors. The method is based on blocking the electrode surface by a thin and compact layer of electronically nonconductive poly(phenylene oxide), PPO, formed by electrochemical polymerization of phenol. Since the phenol polymerization occurs in the potential window where MoS2 is electrochemically inactive, the PPO deposition is area‐selective, limited to the electrode surface. The deposited PPO film is characterized by electrochemical, X‐ray photoelectron spectroscopy, scanning electron microscopy, and atomic force microscopy techniques. The applicability of this method is demonstrated by coating the electrodes of a MoS2‐based field‐effect transistor coupled with a nanopore. The highly selective deposition, the simple approach, and the compatibility with MoS2 makes this method a good strategy for efficient insulation of

Published in: "Advanced Functional Materials".

Kinetic‐Oriented Construction of MoS2 Synergistic Interface to Boost pH‐Universal Hydrogen Evolution

2019-12-10T06:32:28+00:00December 10th, 2019|Categories: Publications|Tags: , , |

The rational design of the interfacial electrocatalyst heterostructure MoS2 is guided by the kinetics investigation. By optimizing the electronic structure based on the simultaneous modulation of the 3d‐band‐offsets of Ni, Co, and Mo near the interface, superior pH‐universal hydrogen evolution performances are achieved, which opens up a new strategy in the design of highly efficient electrocatalysts. Abstract As a prerequisite for a sustainable energy economy in the future, designing earth‐abundant MoS2 catalysts with a comparable hydrogen evolution catalytic performance in both acidic and alkaline environments is still an urgent challenge. Decreasing the energy barriers could enhance the catalysts’ activity but is not often a strategy for doing so. Here, the first kinetic‐oriented design of the MoS2‐based heterostructure is presented for pH‐universal hydrogen evolution catalysis by optimizing the electronic structure based on the simultaneous modulation of the 3d‐band‐offsets of Ni, Co, and Mo near the interface. Benefiting from this desirable electronic structure, the obtained MoS2/CoNi2S4 catalyst achieves an ultralow overpotential of 78 and 81 mV at 10 mA cm−2, and turnover frequency as high as 2.7 and 1.7 s−1 at the overpotential of 200 mV in alkaline and acidic media, respectively. The MoS2/CoNi2S4 catalyst represents one of the best hydrogen evolution reaction performing ones among MoS2‐based catalysts reported to date in both alkaline and acidic environments, and equally important is the remarkable long‐term stability with negligible activity loss after maintaining at 10 mA cm−2 for 48 h in both acid and base. This work highlights the potential to deeply understand and

Published in: "Advanced Functional Materials".

Energy Transport by Radiation in Hyperbolic Material Comparable to Conduction

2019-12-10T06:31:57+00:00December 10th, 2019|Categories: Publications|Tags: , |

Energy transport by electromagnetic waves inside hyperbolic material boron nitride is investigated. A microscopic many‐body model is developed and shows that radiative heat transfer is in the same order of magnitude as phononic heat transfer. Experiments on total thermal transport provide the same conclusion, and radiative transfer accounts for a larger fraction of total energy transport at higher temperatures. Abstract Radiation as a heat transfer mode inside a bulk material is usually negligible in comparison to conduction. Here, the contribution of radiation to energy transport inside a hyperbolic material, hexagonal boron nitride (hBN), is investigated. With hyperbolic dispersion, i.e., opposite signs of dielectric components along principal directions, phonon polaritons contribute significantly to energy transport due to a much greater number of propagating modes compared to that in a normal material. A many‐body model is developed to account for radiative heat transfer in a material with a nonuniform temperature distribution. The total radiative heat transfer through hBN is found to be largely contributed by the high‐κ modes within the Reststrahlen bands, and is comparable to phonon conduction. Experimental measurements of temperature‐dependent thermal transport also show that radiative contribution to thermal transport is of the same order as that from phonons. Therefore, this work shows, for the first time, radiative heat transfer inside a material can be comparable to phonon conductive heat transfer.

Published in: "Advanced Functional Materials".

Grain Boundaries: Nanoassembly Growth Model for Subdomain and Grain Boundary Formation in 1T′ Layered ReS2 (Adv. Funct. Mater. 49/2019)

2019-12-08T12:31:48+00:00December 8th, 2019|Categories: Publications|Tags: |

In article number https://doi.org/10.1002/adfm.2019063851906385, Jinhua Hong, Feng Ding, Hua Xu, and co‐workers reveal a nanoassembly growth model of low symmetry 2D materials to understand the formation mechanism of grain boundaries and subdomains in CVD grown 1T’ ReS2.

Published in: "Advanced Functional Materials".

Grain Boundaries: Nanoassembly Growth Model for Subdomain and Grain Boundary Formation in 1T′ Layered ReS2 (Adv. Funct. Mater. 49/2019)

2019-12-03T14:31:57+00:00December 3rd, 2019|Categories: Publications|Tags: |

In article number https://doi.org/10.1002/adfm.2019063851906385, Jinhua Hong, Feng Ding, Hua Xu, and co‐workers reveal a nanoassembly growth model of low symmetry 2D materials to understand the formation mechanism of grain boundaries and subdomains in CVD grown 1T’ ReS2.

Published in: "Advanced Functional Materials".

Grain Boundaries: Nanoassembly Growth Model for Subdomain and Grain Boundary Formation in 1T′ Layered ReS2 (Adv. Funct. Mater. 49/2019)

2019-12-03T12:31:26+00:00December 3rd, 2019|Categories: Publications|Tags: |

In article number https://doi.org/10.1002/adfm.2019063851906385, Jinhua Hong, Feng Ding, Hua Xu, and co‐workers reveal a nanoassembly growth model of low symmetry 2D materials to understand the formation mechanism of grain boundaries and subdomains in CVD grown 1T’ ReS2.

Published in: "Advanced Functional Materials".

Atomic Mechanisms for the Si Atom Dynamics in Graphene: Chemical Transformations at the Edge and in the Bulk

2019-12-03T06:33:53+00:00December 3rd, 2019|Categories: Publications|Tags: |

Machine learning is applied to study atomic mechanisms for the Si impurity dynamics in graphene from scanning transmission electron microscopy movies. Specifically, deep learning is used to extract atomic features from noisy data, which is followed by a Gaussian mixture model to create a library of the structural descriptors. Then, a Markov model is used to analyze the transition probabilities. Abstract The dynamic behavior of e‐beam irradiated Si atoms in the bulk and at the edges of single‐layer graphene is examined using scanning transmission electron microscopy (STEM). A deep learning network is used to convert experimental STEM movies into coordinates of individual Si and carbon atoms. A Gaussian mixture model is further used to establish the elementary atomic configurations of the Si atoms, defining the bonding geometries and chemical species and accounting for the discrete rotational symmetry of the host lattice. The frequencies and Markov transition probabilities between these states are determined. This analysis enables insight into the defect populations and chemical transformation networks from the atomically resolved STEM data. Here, a clear tendency is observed for the formation of a 1D Si crystal along zigzag direction of graphene edges and for the Si impurity coupling to topological defects in bulk graphene.

Published in: "Advanced Functional Materials".

Self‐Assembling of Conductive Interlayer‐Expanded WS2 Nanosheets into 3D Hollow Hierarchical Microflower Bud Hybrids for Fast and Stable Sodium Storage

2019-12-03T06:33:43+00:00December 3rd, 2019|Categories: Publications|Tags: , |

A three‐dimensional hollow microflower bud‐like structured H‐WS2@NC is prepared by a bottom‐up template‐free self‐assembling solvothermal technique, where nanoflowers’ building block of ultrathin WS2 nanosheets embeds into nitrogen‐doped carbon framework. Such nano‐microstructure provides favorable properties with a highly conductive network, low volume variation, and stable structure toward sodium ions storage, leading to fast kinetics, high reversibility, and cycling stability. Abstract Transition‐metal dichalcogenides have emerged as promising anodes of sodium ion batteries (SIBs). Their practical SIB application calls for an easy‐to‐handle synthetic technique capable of fabricating favorable properties with high conductivity and stable structure. Here, a solvothermal strategy is reported for bottom‐up self‐assembling of nanoflowers’ building block, i.e., conductive interlayer‐expanded 2D WS2 nanosheets thanks to in situ interlayer modification by nitrogen‐doped carbon matrix, into 3D hollow microflower bud‐like hybrids (H‐WS2@NC). The 3D nano/microhierarchical hollow structures are constructed by conductive interlayer‐expanded WS2 nanosheets’ building blocks, providing abundant channels facilitating mass transport/electrons transfer, robust protection layer to avoid the direct contact between WS2 nanosheets and electrolyte, sufficient inner space for accommodating volume variation, and decreased ions diffusion energy barrier for accelerating electrochemical kinetics, as revealed by density functional theory calculations. As such, the 3D H‐WS2@NC hybrids exhibit quite attractive sodium storage performance with high reversible capacity, superior rate capability, and impressively long cycling life. The 3D H‐WS2@NC is further verified as anode of sodium‐ion full cell pairing with Na3V2(PO4)3/rGO cathode, delivering a stable reversible capacity of 296 mAh g−1 at 0.5 A g−1 with high energy density of 128 Wh kg−1total at a power

Published in: "Advanced Functional Materials".

PdTe2 Transition‐Metal Dichalcogenide: Chemical Reactivity, Thermal Stability, and Device Implementation

2019-12-03T06:33:30+00:00December 3rd, 2019|Categories: Publications|Tags: , , |

The chemical and thermal stability of PdTe2 are assessed by experiments and theory, with successive implementation in electronics. Remarkably, the responsivity of a PdTe2‐based millimeter‐wave receiver is 13 and 21 times higher than similar devices based on black phosphorus and graphene in the same operational conditions. Moreover, the PdTe2 surface is stable for one year, with only a sub‐nanometric TeO2 skin formed after air exposure. Abstract Palladium ditelluride (PdTe2) is a novel transition‐metal dichalcogenide exhibiting type‐II Dirac fermions and topological superconductivity. To assess its potential in technology, its chemical and thermal stability is investigated by means of surface‐science techniques, complemented by density functional theory, with successive implementation in electronics, specifically in a millimeter‐wave receiver. While water adsorption is energetically unfavorable at room temperature, due to a differential Gibbs free energy of ≈+12 kJ mol−1, the presence of Te vacancies makes PdTe2 surfaces unstable toward surface oxidation with the emergence of a TeO2 skin, whose thickness remains sub‐nanometric even after one year in air. Correspondingly, the measured photocurrent of PdTe2‐based optoelectronic devices shows negligible changes (below 4%) in a timescale of one month, thus excluding the need of encapsulation in the nanofabrication process. Remarkably, the responsivity of a PdTe2‐based millimeter‐wave receiver is 13 and 21 times higher than similar devices based on black phosphorus and graphene in the same operational conditions, respectively. It is also discovered that pristine PdTe2 is thermally stable in a temperature range extending even above 500 K, thus paving the way toward PdTe2‐based high‐temperature electronics. Finally, it

Published in: "Advanced Functional Materials".

Template‐Assisted Synthesis of Metallic 1T′‐Sn0.3W0.7S2 Nanosheets for Hydrogen Evolution Reaction

2019-12-03T06:33:08+00:00December 3rd, 2019|Categories: Publications|Tags: |

Sn1− xW xS2 alloys are synthesized with 1T SnS2 as the template by adjusting the molar ratios of precursors. The Sn0.3W0.7S2 alloy shows up to 83% metallic properties and possess a distorted octahedral coordination 1T′ phase structure. Metallic 1T′‐Sn0.3W0.7S2 endows a markedly enhanced hydrogen evolution reaction (HER) performance. The auxiliary of carbon black further effectively improves HER, catalytic performance rarely attenuates, and structure morphology remains stable. Abstract Crystal phase control still remains a challenge for the precise synthesis of 2D layered metal dichalcogenide (LMD) materials. The T′ phase structure has profound influences on enhancing electrical conductivity, increasing active sites, and improving intrinsic catalytic activity, which are urgently needed for enhancing hydrogen evolution reaction (HER) activity. Theoretical calculations suggest that metastable T′ phase 2D Sn1− xW xS2 alloys can be formed by combining W with 1T tin disulfide (SnS2) as a template to achieve a semiconductor‐to‐metallic transition. Herein, 2D Sn1− xW xS2 alloys with varying x are prepared by adjusting the molar ratio of reactants via hydrothermal synthesis, among which Sn0.3W0.7S2 displays a maximum of concentration of 81% in the metallic phase and features a distorted octahedral‐coordinated metastable 1T′ phase structure. The obtained 1T′‐Sn0.3W0.7S2 has high intrinsic electrical conductivity, lattice distortion, and defects, showing a prominently improved HER catalytic performance. Metallic Sn0.3W0.7S2 coupled with carbon black exhibits at least a 215‐fold improvement compared to pristine SnS2. It has excellent long‐term durability and HER activity. This work reveals a general phase transition strategy by using T phase materials as templates and merging

Published in: "Advanced Functional Materials".

Cu Intercalation and Br Doping to Thermoelectric SnSe2 Lead to Ultrahigh Electron Mobility and Temperature‐Independent Power Factor

2019-12-03T06:32:59+00:00December 3rd, 2019|Categories: Publications|

A new strategy for enhancing thermoelectric performance for eco‐friendly SnSe2 is demonstrated. Simultaneous Cu intercalation into van der Waals gap and Br doping into SnSe2 lattice electrically bridges otherwise isolated SnSe2 layers, leading to a record high electron mobility, power factor, and engineering ZT for SnSe2. Its highly unusual temperature‐independent power factor is crucially important in stable thermoelectric power generation. Abstract Due to its single conduction band nature, it is highly challenging to enhance the power factor of SnSe2 by band convergence. Here, it is reported that simultaneous Cu intercalation and Br doping induce strong Cu–Br interaction to connect SnSe2 layers, otherwise isolated, via “electrical bridges.” Atom probe tomography analysis confirms a strong attraction between Cu intercalants and Br dopants in the SnSe2 lattice. Density functional theory calculations reveal that this interaction delocalizes electrons confined around SnSe covalent bonds and enhances charge transfer across the SnSe2 slabs. These effects dramatically increase electron mobility and concentration. Polycrystalline SnCu0.005Se1.98Br0.02 shows even higher electron mobility than pristine SnSe2 single crystal and the theoretical expectation. This results in significantly improved electrical conductivity without reducing effective mass and Seebeck coefficient, thereby leading to the highest power factor of ≈12 µW cm−1 K−2 to date for polycrystalline SnSe2 and SnSe. It even surpasses the value for the state‐of‐the‐art n‐type SnSe0.985Br0.015 single crystal at elevated temperatures. Surprisingly, the achieved power factor is nearly independent of temperature ranging from 300 to 773 K. The engineering thermoelectric figure of merit ZTeng for SnCu0.005Se1.98Br0.02 is ≈0.25 between 773 and 300

Published in: "Advanced Functional Materials".

Some say, that 2D Research is the best website in the world.