High Carrier Mobility Research Articles

Performance-related structural, optical, and electrical characteristics of 2 μm the CdTe-CdSe absorption layer of solar cell

The current work attempts to develop the most efficient compositions of 1 m between CdTe1-xSex thin films as absorptive layer in solar cell applications (with x = 0 to 1, step 0.1 wt.%). Mechanical alloying was used to create the CdTe1-xSex powdered materials, and thermal evaporation was used to create the thin film versions of these compositions. Swanepoel's approach was used to measure the films' thicknesses, and the spectroscopic ellipsometry technique was used to calibrate the results. The analyzed films' structural, electrical, and optical characteristics have been studied. It was determined that CdTe0.7Se0.3 at had the highest crystalize size and the lowest lattice strain, which contributed to the reduction in imperfection in this sample since XRD revealed the nanostructures nature of these films. Additionally, it was discovered that CdTe0.7Se0.3 had the lowest energy gap and the highest refractive index, which was responsible for this composition's largest crystalline size. CdTe0.7Se0.3 possessed low resistivity, high conductivity, a high carrier concentration, and high carrier mobility, according to the Hall effect studies of these films. Two different types of solar cells were created: n-CdS/pCdTe and n-CdS/p-CdTe/ CdTe0.7Se0.3. The power conversion efficiency of these two solar cells was determined to be 17.71 for CdS/CdTe and 18.92 for CdS/CdTe/ CdTe0.7Se0.3. Se should be doped in CdTe1-xSex thin films at an ideal level of 0.3%, making CdTe0.7Se0.3 thin film a suitable choice for solar cell applications.

Enhanced Direct Exchange Interaction and Hybridization by Single-Atom Linkers for High Curie Temperature and Superior Visible-Light Harvesting in Cr3(CN3)2.

Designing two-dimensional (2D) ferromagnetic (FM) semiconductors with elevated Curie temperature, high carrier mobility, and strong light harvesting is challenging but crucial to the development of spintronics with multifunctionalities. Herein, we show first-principles computation evidence of the 2D metal-organic framework Kagome ferromagnet Cr3(CN3)2. Monolayer Cr3(CN3)2 is predicted to be an FM semiconductor with a record-high Curie temperature of 943 K owing to the use of a single-atom linker (N), which results in strong direct d-p exchange interaction and hybridization between dyz/xz and pz of Cr and N, as well as excellent matching characteristics in energy and symmetry. The single-atom linker structural feature also leads to notable band dispersion and a relatively high carrier mobility of 420 cm2 V-1 s-1. Moreover, under the in-plane strain, 2D Cr3(CN3)2 can be tuned to possess a strong visible-light-harvesting functionality. These novel properties render monolayer Cr3(CN3)2 a distinct 2D ferromagnet with high potential for the development of multifunctional spintronics.

Effect of Hyperconjugation on Photovoltaic Performance in Pseduo‐2D Perylene Diimide Derivatives†

Comprehensive SummaryThe π‐π interaction is acknowledged as the predominant factor to determine the molecular packing in organic photovoltaic materials, while other non‐covalent intermolecular interactions especially the σ‐π hyperconjugation are often ignored. Herein, a perylene diimide (PDI) derivative named FIDT‐PDI is designed and synthesized to shed light into the effect of hyperconjugation on the molecular packing and further the photovoltaic performance. Dynamic NMR and 2D NOE NMR demonstrate the formation of intermolecular σ‐π hyperconjugation between the C—H bond of the PDI moiety in one molecule and the phenyl sidechain in another molecule of FIDT‐PDI. Benefiting from the σ‐π hyperconjugation, FIDT‐PDI with twisted backbone reversely exhibits more ordered packing and stronger crystallinity compared with another PDI derivative FIDTT‐PDI which has better planarity, consequently achieving superior PCE and higher carrier mobility. This contribution is the first paradigm to unravel the structure‐property relationship between σ‐π hyperconjugation of conjugated materials and corresponding photovoltaic performance.

Advances in separation of monochiral semiconducting carbon nanotubes and the application in electronics

For over half a century, traditional silicon-based integrated circuits (ICs) have been the basis of computational electronics and are widely used in computers, cell phones, and other fields. With the rapid development of human society, silicon-based semiconductor technology is approaching its physical and engineering limits. Our increasing diversity of non-traditional computing needs, such as ultra-small, ultra-fast, ultra-low-power wearables, and space radiation protection, is driving the search for new electronic materials. Semiconducting single-walled carbon nanotubes (s-SWCNTs) have many excellent electrical properties, such as high carrier mobility and high ballistic transport, making them strong candidates for new semiconductor materials in the post-Moore era. Carbon-based electronic technology has been developed for over 20 years, and the fundamental issues such as the material purification of s-SWCNTs, preparation prospects of s-SWCNT-based field-effect transistors (CNT FETs), and device physics based on CNT FETs have been basically solved. However, the chiral diversity of s-SWCNTs may lead to problems such as fluctuations in the electrical performance of CNT FETs, limiting the application of s-SWCNTs in high-end ICs. Monochiral s-SWCNTs not only have excellent electrical properties but also have a controllable structure and uniformity, which are crucial for the high-end IC of CNTs. However, some problems exist in the purity and yield of monochiral s-SWCNT preparation and the optimization of monochiral CNT FETs. Therefore, the chiral sorting of CNTs is reviewed in this paper, and the progress of polymer reprocessing in chiral separation is highlighted. Then, the research progress of monochiral CNT FETs is introduced, and possible development directions are summarized and analyzed. Finally, the application prospects of chiral-enriched s-SWCNTs include challenges and future opportunities.

SnS2/MoS2 van der Waals Heterostructure Photodetector with Ultrahigh Responsivity Realized by a Photogating Effect.

Photoresponsivity is a fundamental parameter used to quantify the ability of photoelectric conversion of a photodetector device. High-responsivity photodetectors are essential for numerous optoelectronic applications. Due to the strong light-matter interactions and the high carrier mobility, two-dimensional (2D) materials are promising candidates for the next-generation photodetectors. However, poor light absorption, lack of photoconductive gain, and the interfacial recombination lead to the relatively low responsivity of 2D photodetectors. The photogating effect, which extends the lifetime of photoexcited carriers, provides a simple approach to enhance responsivity in photodetector devices. Here, the O2 plasma treatment introduced surface traps on the SnS2 surface, leading to a gate-tunable photogating effect in SnS2/MoS2 heterojunctions. The heterojunction device exhibits an ultrahigh responsibility of up to 28 A/W. Moreover, the photodetector possesses a wide spectral photoresponse spanning from 300 to 1100 nm and a high specific detectivity (D*) of 4 × 1011 Jones under a 532 nm laser at VDS = 1 V. These results demonstrate that O2 plasma treatment is an efficient and simple avenue to achieve photogating effects, which can be employed to enhance the performance of van der Waals heterostructure photodetector devices and make them suitable for future integration into advanced electronic and optoelectronic systems.

Small Molecule Additives to Suppress Bundling in Dimensional‐Limited Self‐Alignment Method for High‐Density Aligned Carbon Nanotube Array

AbstractSemiconducting single‐walled carbon nanotube (CNT) is a promising candidate as a channel material for advanced logic transistors, attributed to the ultra‐thin 1‐nm cylindrical geometry, high mobility, and high carrier injection velocity. However, the presence of undesired CNT bundles in the CNT arrays for wafer‐scale device fabrication, even when utilizing the state‐of‐the‐art dimension‐limited self‐alignment (DLSA) method, poses challenges. These CNT bundles degrade the transistor gate's efficiency in controlling the flow of charge carriers in the CNT channel, leading to pronounced device‐to‐device variability. Here, a novel method is introduced to alleviate bundling in CNT arrays assembled via DLSA, by involving small molecule additive to screen the attractive van der Waals force between neighboring CNTs during the DLSA process, resulting in over 50% reduction in CNT bundling. Furthermore, a pioneering methodology for quantifying CNT bundles is presented and employed experimentally to assess bundles in dense CNT arrays assembled by DLSA using transmission electron microscopy. Both experimental data and molecular dynamics simulation reveal that CNT bundling originates from van der Waals attraction between CNTs, and the disturbed liquid‐liquid interface by accumulating excess polar molecules. These findings illuminate new pathways for realizing dense, bundle‐free CNT arrays.

Highly stretchable polymer semiconductor thin films with multi-modal energy dissipation and high relative stretchability

Stretchable polymer semiconductors (PSCs) have seen great advancements alongside the development of soft electronics. But it remains a challenge to simultaneously achieve high charge carrier mobility and stretchability. Herein, we report the finding that stretchable PSC thin films (<100-nm-thick) with high stretchability tend to exhibit multi-modal energy dissipation mechanisms and have a large relative stretchability (rS) defined by the ratio of the entropic energy dissipation to the enthalpic energy dissipation under strain. They effectively recovered the original molecular ordering, as well as electrical performance, after strain was released. The highest rS value with a model polymer (P4) exhibited an average charge carrier mobility of 0.2 cm2V−1s−1 under 100% biaxial strain, while PSCs with low rS values showed irreversible morphology changes and rapid degradation of electrical performance under strain. These results suggest rS can be used as a parameter to compare the reliability and reversibility of stretchable PSC thin films.

Interfacial P–O covalent bonds regulated electronic configuration in black phosphorus for improving oxygen evolution activity

Black phosphorus (P(black)) shows impressive physicochemical features for electrocatalysis including adjustable bandgap and high charge carrier mobility. However, the existence of solitary electron pairs in exfoliated P(black) nanosheets (EP(black)) leads to rapid surface degradation, resulting in unfavorable durability. Herein, a P–O bridge was created in the heterostructure EP(black)/vanadium-doped cobalt hydroxide with oxygen vacancy (EP(black)/V–CoO2-xH2) to stabilize and expedite oxygen evolution reaction (OER) activity. By bonding the solitary electron pairs of EP(black) and oxygen species (OH*) of V–CoO2-xH2, the distinctive P–O bridge resulted in important ligand effects that improved not merely the stability of EP(black) but effectively regulated the electron configuration of V–CoO2-xH2. DFT simulations revealed that directional interfacial electron migration from V–CoO2-xH2 to EP(black) facilitated the formation of pivotal OER intermediates and hence boosted OER activities. This study proposes a novel strategy to enhance the electrochemical properties of EP(black), which could be extended to a wide range of high-performance electrocatalyst systems.

A Review on Carrier Mobilities of Epitaxial Graphene on Silicon Carbide.

Graphene growth by thermal decomposition of silicon carbide (SiC) is a technique that produces wafer-scale, single-orientation graphene on an insulating substrate. It is often referred to as epigraphene, and has been thought to be suitable for electronics applications. In particular, high-frequency devices for communication technology or large quantum Hall plateau for metrology applications using epigraphene are expected, which require high carrier mobility. However, the carrier mobility of as-grown epigraphene exhibit the relatively low values of about 1000 cm2/Vs. Fortunately, we can hope to improve this situation by controlling the electronic state of epigraphene by modifying the surface and interface structures. In this paper, the mobility of epigraphene and the factors that govern it will be described, followed by a discussion of attempts that have been made to improve mobility in this field. These understandings are of great importance for next-generation high-speed electronics using graphene.

Extremely large magnetoresistance and quantum oscillations in semimetal Ni3In2S2

In this work, we present magnetotransport properties and quantum oscillations in single-crystalline shandite compound Ni3In2S2, which is a recently identified semimetal with endless Dirac-nodal lines. Ni3In2S2 displays a giant transverse magnetoresistance of ∼24 000 % at 2 K and 14 T and a magnetic field-induced resistivity upturn behavior at low temperatures. Below 50 K, the magnetoresistance curves show a linear magnetic field dependence under high magnetic fields. The computation results indicate that Ni3In2S2 is a semimetal with linear crossings near the Fermi level. The small effective mass, deduced from de Haas–van Alphen quantum oscillations, suggests the high carrier mobility in Ni3In2S2. The high mobility and quantum linear magnetoresistance resulting from the linear dispersive bands jointly lead to the extreme transverse magnetoresistance in our Ni3In2S2 crystal. Our findings can be a reference to understand and search for semimetals with extreme magnetoresistance.

Extremely large magnetoresistance and non-trivial band topology in YSb semimetal

The topologically protected states in a material lead to the occurrence of spectacular properties like massless fermions, high carrier mobility, extremely large magnetoresistance (XMR) and nontrivial Berry phase. In this context, we report the experimental realization of non-trivial band topology and nonsaturating XMR at low temperatures in a rock-salt type rare-earth monopnictide YSb semimetal which is ∼ two million percent at 2 K and 9 T. The Hall resistivity and Shubnikov-de Hass (SdH) oscillations confirm the multiband character of YSb crystal along with high carrier mobility. The analysis of SdH oscillations reveal a π-Berry phase for the α-band, indicating the non-trivial band topology in YSb. This non-trivial band topology is further confirmed by the observation of the topologically protected state, which is demonstrated by a high transport lifetime (τtr) to the quantum lifetime (τq) ratio, r = τtrτq = 300 times. The topological protection results in a very low zero-field resistivity at low temperatures. Here, we show that the topological protection mechanism, charge compensation and high carrier mobility are the key factors for obtaining XMR in YSb crystal.

SPICE model of MoS2/p-Si photodiode

Molybdenum disulfide (MoS2) 2D-material is considered as one of potential candidates for next generation optoelectronic devices due to its tunable bandgap, relatively high carrier mobility, and good light absorption, etc. From the perspective of circuit simulation and system verification, an equivalent circuit model of MoS2/p-Si photodiode is required. In the paper, the optical response and the carrier transmission process of MoS2/p-Si photodiode are analyzed theoretically. A SPICE (Simulation Program with Integrated Circuit Emphasis) equivalent circuit model of MoS2/p-Si photodiode is proposed, which can be used to simulate the photoelectric characteristics of the 2D device. Based on the established SPICE model of MoS2/p-Si photodiode, the simulation results are consistent with the experimental results of MoS2/p-Si photodiode devices. The trans-impedance amplifier (TIA) is designed for MoS2/p-Si photodiode, and the set-up SPICE model is used to verify the designed TIA circuit. It shows that the SPICE model has potential application for the simulation of the opto-electrical system including the cutting-edge 2-D photo diode.

High-Performance Wearable Organic Photodetectors by Molecular Design and Green Solvent Processing for Pulse Oximetry and Photoplethysmography.

White-light detection from the visible to the near-infrared region is central to many applications such as high-speed cameras, autonomous vehicles, and wearable electronics. While organic photodetectors (OPDs) are being developed for such applications, several challenges must be overcome to produce scalable high-detectivity OPDs. This includes issues associated with low responsivity, narrow absorption range, and environmentally friendly device fabrication. Here, an OPD system processed from 2-methyltetrahydrofuran (2-MeTHF) sets a record in light detectivity, which is also comparable with commercially available silicon-based photodiodes is reported. The newly designed OPD is employed in wearable devices to monitor heart rate and blood oxygen saturation using a flexible OPD-based finger pulse oximeter. In achieving this, a framework for a detailed understanding of the structure-processing-property relationship in these OPDs is also developed. The bulk heterojunction (BHJ) thin films processed from 2-MeTHF are characterized at different length scales with advanced techniques. The BHJ morphology exhibits optimal intermixing and phase separation of donor and acceptor moieties, which facilitates the charge generation and collection process. Benefitting from high charge carrier mobilities and a low shunt leakage current, the newly developed OPD exhibits a specific detectivity of above 1012 Jones over 400-900nm, which is higher than those of reference devices processed from chlorobenzene andortho-xylene.

Rapid, one-step thermolysis synthesis of large-scaled molybdenum disulfide thin films with high mobility

In this study, a simple and rapid method for the synthesis of molybdenum disulfide (MoS2) through thermolysis was demonstrated. In the previous reported work, the thermolysis synthesis of MoS2 usually required a two-step process. The process is time-consuming, and need high-temperature (900 °C). In this study, we synthesize large-area thin films quickly in a single step at 450 °C using both hydrogen gas and sulfur powders for synthesis and defect filling at the same time. The layer number of MoS2 films, controlled by the precursor concentration, is determined to be between 3 and 10 layers via Raman spectroscopy and TEM analysis. XPS analysis revealed the optimal amount of sulfur powders for vacancy refilling, and films prepared with this amount exhibited high carrier mobility of up to 220 cm2/Vs. According to the author's knowledge, the carrier mobility of proposed samples is much higher than that of the reported data.

Role of Ag and g-C3N4 over CaTiO3 for effective photocatalytic degradation of nitrobenzene

In the present study, g-C3N4/CaTiO3 (GCT) heterostructure with various Ag contents have been synthesized via simple hydrothermal method and characterized using various instrumental techniques. Stability of synthesized samples was measured by thermogravimetric analysis (TGA) and zeta potential measurement. The photocatalytic activity of all the synthesized was evaluated by the degradation of nitrobenzene (NB) in aqueous media. The photocatalytic activity of heterostructure AGCT was observed enhanced under the light irradiation. This would be attributed to the suitable band structure, resulting in the efficient charge separation and transfer of photogenerated charge carriers. The final percentage of degradation was observed 70% with AGCT5 and 64% with AGCT1 which were highest among other catalysts applied after 2 h. The Ag doping in CT catalyst led to antagonist performance, and to better degradation of NB. The multivalency of Ag leads to prevent agglomeration and recombination of electrons and holes and transferring them from Ag to Ca. The reaction rate (2.36 × 10−3 molL−1 min−1 at 20 °C) and percentage degradation (∼70%) were observed to get increased with the increase in the temperature with the apparent activation energy of 40.3 kJ/mol. The enhanced performance at increased temperature was attributed to overcome the energy of activation and high mobility of charge carriers.

Recent Advances in Nanowire-Based Wearable Physical Sensors.

Wearable electronics is a technology that closely integrates electronic devices with the human body or clothing, which can realize human-computer interaction, health monitoring, smart medical, and other functions. Wearable physical sensors are an important part of wearable electronics. They can sense various physical signals from the human body or the surrounding environment and convert them into electrical signals for processing and analysis. Nanowires (NW) have unique properties such as a high surface-to-volume ratio, high flexibility, high carrier mobility, a tunable bandgap, a large piezoresistive coefficient, and a strong light-matter interaction. They are one of the ideal candidates for the fabrication of wearable physical sensors with high sensitivity, fast response, and low power consumption. In this review, we summarize recent advances in various types of NW-based wearable physical sensors, specifically including mechanical, photoelectric, temperature, and multifunctional sensors. The discussion revolves around the structural design, sensing mechanisms, manufacture, and practical applications of these sensors, highlighting the positive role that NWs play in the sensing process. Finally, we present the conclusions with perspectives on current challenges and future opportunities in this field.

Correlating Carrier Dynamics with Performance in Perovskite Solar Cells

Advancing the efficiency of perovskite solar cells (PSCs) critically depends on suppressing non‐radiative recombination at perovskite‐related interfaces and within the perovskite layer. A comprehensive understanding of carrier dynamic within PSCs is pivotal for promoting their efficiencies and facilitating more flexible design options for both perovskite and transport layers. Herein, the intrinsic mechanisms and device physics of PSCs are delved into, with a specific focus on investigating the variation of electron and hole mobilities and their effects on device performance. Through a rigorous photoelectric simulation, it is confirmed that the impact of performance of PSCs on electron or hole mobility primarily depends on the direction of illumination. For n–i–p PSCs, high hole mobility is favorable for the device performance, whereas for p–i–n PSCs, elevated electron mobility proves advantageous. Notably, these findings remain applicable across a large range of transport layers and perovskite bandgaps, although exceptions may arise when the perovskite layer undergoes specific doping. Additionally, it is discovered that high carrier mobility contributes to the reduction of both carrier and ion accumulation, thereby effectively suppressing hysteresis behavior. In this work, valuable insights into the significance and mechanisms of carrier mobility in PSCs are provided, offering essential guidance for fabricating high‐efficiency PSCs.

Tinite–Ceramic‐Inspired Solar‐Driven Thermoelectric Nanogenerator—Single Step toward Efficient Energy Harvesting

One of the promising approaches is solar radiation and thermal energy can be converted into electricity using photothermoelectric materials. Ceramic‐inspired photothermoelectric materials are extensively researched in the quest for efficient and sustainable energy conversion technologies. Herein, the synthesis and utilization of titanium nitride (known as tinite–ceramic) nanoparticles used first in two specific applications are reported: solar‐driven thermoelectric nanogenerators and photothermal‐based evaporation applications. The nanogenerator is innovatively fabricated via a UV‐induced deposition technique. The tinite–ceramic possesses excellent solar absorption (92.5%) and subsequent photothermally converted heat (39.9 °C) under 1 kW m−2 solar irradiation for an effective solar energy harvesting candidate. The complimentary nanogenerator endows high carrier mobility and effective photothermal‐to‐electric energy conversion (short‐circuit current, Iout = 58.8 mA) under 2 kW m−2 solar irradiation. The switchable nanogenerator maintains its reproducibility under different cycles, tailoring its tunability under different solar irradiation. More interestingly, a tinite–ceramic‐inspired solar evaporator exhibits an evaporation rate of up to 2.02 kg m−2 h−1 under 1 kW m−2 solar irradiation. Titanite's dual functionality offers the potential to revolutionize how renewable energy sources are harnessed and utilized for environmentally friendly and sustainable energy production.

High-Mobility Topological Semimetals as Novel Materials for Huge Magnetoresistance Effect and New Type of Quantum Hall Effect.

The quantitative description of electrical and magnetotransport properties of solid-state materials has been a remarkable challenge in materials science over recent decades. Recently, the discovery of a novel class of materials-the topological semimetals-has led to a growing interest in the full understanding of their magnetotransport properties. In this review, the strong interplay among topology, band structure, and carrier mobility in recently discovered high carrier mobility topological semimetals is discussed and their effect on their magnetotransport properties is outlined. Their large magnetoresistance effect, especially in the Hall transverse configuration, and a new version of a three-dimensional quantum Hall effect observed in high-mobility Weyl and Dirac semimetals are reviewed. The possibility of designing novel quantum sensors and devices based on solid-state semimetals is also examined.

Structural engineering of two-dimensional black phosphorus towards advanced photonic integrated circuits

Structural engineering is crucial for tuning the properties of artificial materials. As one of the most important two-dimensional (2D) materials, black phosphorus (BP) has been rediscovered in 2014 and attracted tremendous attentions all over the world. It shows great potentials in optoelectronic and integrated photonic applications due to the direct and tunable bandgap, high carrier mobility, and intrinsic anisotropy. However, some deficiencies are yet to be settled before its large-scale applications, such as the massive synthesis methods and structure–property relationship. To investigate the influence of structural engineering on the performance of 2D BP-based devices thoroughly, recent studies on deformation, atomic defects, superlattice, alloying, thickness and phase transition are maximality summarized in this review covering from the intrinsic properties to optoelectronic applications. Benefiting from the broad research in this field, challenges and opportunities of 2D BP for advanced integrated photonic applications are also provided, which supplies a useful reference to realize large-scale 2D BP-based all-optical communications in future.