Device passivation through ultraclean hexagonal BN encapsulation has proven to be one of the most effective ways of constructing high-quality devices with atomically thin semiconductors that preserve ...the ultraclean interface quality and intrinsic charge transport behavior. However, it remains challenging to integrate lithography-compatible contact electrodes with flexible distributions and patterns. Here, we report the feasibility of a straightforward integration of lithography-defined contacts into BN-encapsulated two-dimensional field-effect transistors (2D FETs), giving rise to overall device quality comparable to the state-of-the-art results from the painstaking pure dry transfer processing. The electronic characterization of FETs consisting of WSe2 and MoS2 channels reveals an extremely low scanning hysteresis of ∼2 mV on average, a low density of interfacial charged impurities of ∼1011 cm–2, and generally high charge mobilities over 1000 cm2 V–1 s–1 at low temperatures. The overall high device qualities verify the viability of directly integrating lithography-defined contacts into BN-encapsulated devices to exploit their intrinsic charge transport properties for advanced electronics.
Metal‐organic frameworks (MOFs) are highly versatile materials owing to their vast structural and chemical tunability. These hybrid inorganic–organic crystalline materials offer an ideal platform to ...incorporate light‐harvesting and catalytic centers and thus, exhibit a great potential to be exploited in solar‐driven photocatalytic processes such as H2 production and CO2 reduction. To be photocatalytically active, UV–visible optical absorption and appropriate band alignment with respect to the target redox potential is required. Despite fulfilling these criteria, the photocatalytic performance of MOFs is still limited by their ability to produce long‐lived electron–hole pairs and long‐range charge transport. Here, a computational strategy is presented to address these two descriptors in MOFs and to translate them into charge transfer numbers and effective mass values. The approach is applied to 15 MOFs from the literature that encompass the main strategies used in the design of efficient photocatalysts including different metals, ligands, and topologies. The results capture the main characteristics previously reported for these MOFs and enable to identify promising candidates. In the quest of novel photocatalytic systems, high‐throughput screening based on charge separation and charge mobility features are envisioned to be applied in large databases of both experimentally and in silico generated MOFs.
Metal‐organic frameworks have great potential to be used as photocatalysts due to their ability to combine photosensitizers with catalytic centers within a porous structure. Charge separation and charge carrier mobility are crucial steps controlling the conversion efficiency in photocatalysis. Herein, a computational approach is presented to quantify these two characteristics in terms of charge transfer numbers and effective mass values.
•Understanding graphene structure and properties can help in grasping the idea of graphene in suitable consideration and applications.•Integration of graphene in fuel cells and batteries have shown a ...better enhancement in the performance and efficiency.•Developing further advanced studies and researches on graphene can be a potential material in renewable energy sector.•Overcoming the main challenges of graphene materials will make it the best candidate for any application especially in energy field.
Energy demand is increasing in the present world where it is essential to explore alternative energy resource that is clean, renewable and sustainable. Graphene is now receiving the great attention as it possesses excellent properties such as high charge mobility up to 230,000 cm2/Vs, 3000 W/m.K thermal conductivity, 2.3% absorption of visible light, strong mechanical strength of 130 GPa and high specific surface area of 2600 m2/g. These properties can be altered depending on synthesis techniques to obtain graphene such as; mechanical exfoliation, reduction of graphene oxide, chemical vapour deposition (CVD) and epitaxial growth of graphene. Furthermore, different characteristics of graphene can be employed for different applications in energy conversion and storage, for example, fuel cell and lithium ion battery. Hence, many studies were investigated to examine graphene and its applications. The objectives of this review is to understand and cover graphene background including properties and synthesis, which will help in understanding better the concept of graphene in its application such as in fuel cell and lithium ion batteries. In addition, it is showing the most key challenges and future consideration when nanostructured graphene is utilized.
We present a novel method to significantly enhance the thermoelectric performance of ceramics in the model system SrTi0.85Nb0.15O3 through the use of the precursor ammonium tetrathiomolybdate (0.5–2% ...w/w additions). After sintering the precursor-infused green body at 1700 K for 24 h in 5% H2/Ar, single-crystal-like electron transport behavior developed with electrical conductivity reaching ∼3000 S/cm at ∼300 K, almost a magnitude higher than that in the control sample. During processing, the precursor transformed into MoS2, then into MoO x , and finally into Mo particles. This limited grain growth promoted secondary phase generation but importantly helped to reduce the grain boundary barriers. Samples prepared with additions of the precursor exhibited vastly increased electrical conductivity, without significant impact on Seebeck coefficients giving rise to high power factor values of 1760 μW/mK2 at ∼300 K and a maximum thermoelectric figure-of-merit zT of 0.24 at 823 K. This processing strategy provides a simple method to achieve high charge mobility in polycrystalline titanate and related materials and with the potential to create “phonon-glass-electron-crystal” oxide thermoelectric materials.
Solid-state lithium–oxygen batteries (SSLOBs) with high energy density and enhanced safety are promising for green energy storage but plagued by limited O2/Li+/e– triple-phase reaction zone and high ...internal resistance. Herein, we design and fabricate a novel SSLOB with an integrated cathode and electrolyte structure in which carbon nanotubes were uniformly coated by an in situ-formed hybrid polymer electrolyte (HPE). This interface engineering builds a three-dimensional hybrid electronic and ionic conductor with sufficient void spaces, which facilitates oxygen diffusion and product accommodation and contributes to a significant expansion of the triple-phase reaction zone. The HPE is prepared in situ from poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), trimethyl phosphate (TMP), and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) via weak hydrogen bond interactions and shows a flame-resistant property and high electrochemical stability (until 5.4 V). More importantly, it exhibits both a high ionic conductivity (1.08 × 10–3 S cm–1) and high lithium ion transference number (t Li + up to 0.73) at ambient temperature, promoting uniform Li deposition. In consequence, the battery displays a gravimetric energy density of 542.1 Wh kg–1 (calculated from the weight of the whole device), superior rate performance, and long cycle life (1000 cycles, 167 days). These systems may promote the practical application of SSLOBs in next-generation energy storage.
Discotic (disk-shaped) molecules or molecular aggregates may form, within a certain temperature range, partially ordered phases, known as discotic liquid crystals, which have been extensively studied ...in the recent past. On the one hand, this interest was prompted by the fact that they represent models for testing energy and charge transport theories in organic materials. However, their long-range self-assembling properties, potential low cost, ease of processability with a variety of solvents and the relative ease of tailoring their properties via chemical synthesis, drove the attention of researchers also towards the exploitation of their semiconducting properties in organic electronic devices. This review covers recent research on the charge transport properties of discotic mesophases, starting with an introduction to their phase structure, followed by an overview of the models used to describe charge mobility in organic substances in general and in these systems in particular, and by the description of the techniques most commonly used to measure their charge mobility. The reader already familiar or not interested in such details can easily skip these sections and refer to the core section of this work, focusing on the most recent and significant results regarding charge mobility in discotic liquid crystals.
Nanocomposite consisting of 5 mol% crystalline CuI-doped hydroxyapatite (HA) was prepared for the first time by facile chemical method and calcined at different temperatures such as 300 °C, 500 °C, ...700 °C and 900 °C. In this study, HA played a role as the matrix and CuI was the reinforcement. The effect of calcination temperature on XRD pattern, TEM, SEM, BET, FTIR, luminescence intensity, photoluminescence quantum yield (PLQY), fluorescence lifetime, charge mobility measurements, electronic speckle pattern interferometry and mechanical properties were investigated. The modified Scherrer equation of the composites showed that the size of the particles increased with increasing calcination temperature from 66.64 to 87.20 nm. The photoluminescence intensity of CuI (5 mol%)/HA was quenched at room temperature, while the represented constant decay time for the calcined compound was increased at 700 °C. Furthermore, the CIE coordinates were shown 0.39333, 0.18493 for CuI (5 mol%)/HA calcined at 700 °C. The charge mobility values of the nanocomposites were extracted by space-charge limited current (SCLC) method and the range of effective mobility was from 3.645 × 10−4 to 6.697 × 10−4 cm2V−1s−1. Mechanical properties were fully discussed via ASTM-E9 standard and CuI (5 mol%)/HA calcined at 900 °C was in better range than other compounds, the σyc and hardness values were reported 7.32 Mpa and 40.81 HV respectively. Speckle interferometry was used to demonstrate that there was no large imperfection in the surface of each sample. The components were very sensitive to the calcination temperatures. In other words, the combination of CuI (5 mol%)/HA showed that the replacement of Cu ions with Ca was helpful to improve the photophysical and mechanical properties.
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•Facile synthesis of the CuI (5 mol%)–doped HA was performed.•The effect of calcination temperatures at 300 °C, 500 °C, 700 °C and 900 °C on the photophysical and mechanical properties was investigated.•Most of the properties was increased with increasing calcination temperature at 700 °C.•The effective hole mobility was found by SCLC method and the values recorded in the range from 3.645 × 10−4 to 6.697 × 10−4 cm2V−1s−1.
Thin‐film transistors (TFTs) based on a new n‐channel organic semiconductor (DCMT; see Figure) are reported. An electron mobility as high as 0.2 cm2/V s was observed, as well as ambipolar TFT ...behavior. Variable temperature measurements reveal that electron conduction is activated, with a small activation energy of 35 ± 10 meV. These results demonstrate that quinoidal oligothiophenes are a promising new class of organic semiconductors for TFTs.
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All-wrapped transistors consisting of two-dimensional transition-metal dichalcogenide channels are appealing candidates for post-silicon electronics. Based on the Boltzmann transport ...theory, here we report a comprehensive theoretical survey on the performance limits for monolayer MoS2 transistors with three prototypical gate dielectrics (Al2O3, HfO2 and BN), by including primary extrinsic charge scattering mechanisms present in practical devices. A concept of “dead space” between the dielectrics and channels is proposed and used in calculation to ameliorate the general overestimation in scattering intensity of surface optical phonons, which enables an accurate description of electronic transport behavior. Crucial device indices, including charge mobility and current density, are thoroughly analyzed for transistors at post-silicon technological nodes beyond 1 nm. The on-state current is estimated to be generally greater than 2 mA μm−1 at channel lengths below 10 nm. The results clarify the potential benefits in performance from extremely miniaturized monolayer-channel transistors for More-Moore electronics.
Asymmetric 5-H-dithieno3,2-b:2′,3′-dpyran (DTP) possessing the stronger electron-donating ability than its analogue 4H-cyclopenta2,1-b:3,4-bʹdithiophene (CPDT) was widely applied in fullerene-based ...solar cells and/or constructed the A-D-A type nonfullerene-based small molecular acceptors. However, limited efforts have devoted to develop perylene-diimide (PDI)-based polymeric acceptors in the field of all-polymer solar cell (All-PSCs). Herein, two donor-acceptor (D-A) type N,N-bis(2-hexyldecyl)-PDI-based polymer acceptors, PPDI-CPDT and PPDI-DTP utilizing 4,4-bis(2-ethylhexyl)-CPDT and 5,5-bis(4-hexylphenyl)-DTP as D moiety, were synthesized. Replacing CDT donor moiety with DTP led to the decreased thermal- and photo-stability. Regardless of an enhanced absorption around 500 nm and 0.02 eV up-shifted ELUMO, however, decreased VOC from 0.79 to 0.56 V and down-shifted JSC from 8.18 to 1.89 mA cm−2, fallen FF from 40.80% to 28.48% and thus 87.79% decreased PCE from 2.62% to 0.30% were observed. The great drop of device efficiency was mainly attributed to the weak aggregation and interaction as a result of inserting the large electronegative oxygen into the inner penta-ring of CPDT unit, which resulted in insufficient separation and restricted the photocurrent and efficient charge transfer process. These researching results suggested that it should be cautious to introduce the strong electron-rich moiety to tune the optoelectronic property and aggregation for obtaining the boosted device efficiency in All-PSCs.
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•Replacing donor moiety CPDT with DTP in PDI-based D-A polymer acceptors decreased thermal- and photo-stability.•Decreased PCE from 2.62% to 0.30% was due to fallen VOC, JSC and FF, despite improved absorption and up-shifted ELUMO.•The greatly dropped PCE was due to weakened aggregation of inserting oxygen into CPDT unit.
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