Efficient Doping Research Articles

Ultra‐Low Threshold Voltage in N‐Type Organic Electrochemical Transistors Enabled by Organic Mixed Ionic‐Electronic Conductors with Dual Electron‐Withdrawing Substitutions

AbstractAchieving low threshold voltage (Vth) in organic electrochemical transistors (OECTs) is essential for minimizing power consumption and enhancing sensitivity in bioelectronic devices. However, obtaining OECT materials with ultra‐low Vth, close to 0 V for n‐type conjugated polymers remains challenging. Here, a conjugated polymer FBDOPV‐CNTVT is introduced, which features a rigid backbone structure and high electron deficiency, leading to an exceptionally low lowest unoccupied molecular orbital (LUMO) energy level of −4.67 eV, achieved through dual electron‐withdrawing substitutions. With its ultra‐low LUMO energy level, FBDOPV‐CNTVT exhibits high susceptibility to electrochemical doping, even demonstrating efficient doping near 0 V. Consequently, the OECT device employing FBDOPV‐CNTVT as the active material shows an ultra‐low Vth of 7.5 mV, setting a new record for the Vth of n‐type OECT devices. Furthermore, FBDOPV‐CNTVT exhibits a µC* value of 6.13 F cm−1 V−1 s−1 and retains ≈85% of its current after 2000 s cycling. This study highlights the potential of conjugated polymers with dual electron‐withdrawing substitutions to achieve ultra‐low LUMO energy levels, effectively reducing the Vth of n‐type OECT devices and promising advancements in bioelectronics.

Interplay between metavalent bonds and dopant orbitals enables the design of SnTe thermoelectrics

Engineering the electronic band structures upon doping is crucial to improve the thermoelectric performance of materials. Understanding how dopants influence the electronic states near the Fermi level is thus a prerequisite to precisely tune band structures. Here, we demonstrate that the Sn-s states in SnTe contribute to the density of states at the top of the valence band. This is a consequence of the half-filled p-p σ-bond (metavalent bonding) and its resulting symmetry of the orbital phases at the valence band maximum (L point of the Brillouin zone). This insight provides a recipe for identifying superior dopants. The overlap between the dopant s- and the Te p-state is maximized, if the spatial overlap of both orbitals is maximized and their energetic difference is minimized. This simple design rule has enabled us to screen out Al as a very efficient dopant to enhance the local density of states for SnTe. In conjunction with doping Sb to tune the carrier concentration and alloying with AgBiTe2 to promote band convergence, as well as introducing dislocations to impede phonon propagation, a record-high average ZT of 1.15 between 300 and 873 K and a large ZT of 0.36 at 300 K is achieved in Sn0.8Al0.08Sb0.15Te-4%AgBiTe2.

Narrowband Electroluminescence from Color Centers in Hexagonal Boron Nitride.

Defects in wide bandgap materials have emerged as promising candidates for solid-state quantum optical technologies. Electrical excitation of single emitters may lead to scalable on-chip devices and therefore is highly sought after. However, most wide bandgap materials are not amenable to efficient doping, posing challenges for electrical excitation and on-chip integration. Here, we demonstrate narrowband electroluminescence from visible and near-infrared color centers in hexagonal boron nitride (hBN). We harness van der Waals tunnel junctions of graphene-hBN-graphene. Charge carriers are electrically injected into hBN, exciting localized defects that emit nonclassical light, as characterized by the second order correlation measurement. Remarkably, the devices operate at room temperature and produce robust, narrowband emission spanning from visible to the near-infrared. Our work marks an important milestone in vdW materials and their promising attributes for integrated quantum technologies and on-chip photonic circuits.

Enhancing Conductivity of Nickel Oxide to Achieve Scalable Preparation for High-Efficiency Perovskite Solar Modules

NiOx, prepared via the sputtering method, exhibits low conductivity and energy level mismatch with the perovskite layer, thereby limiting further enhancements in the performance of perovskite solar modules (PSMs). Unlike traditional methods that enhance the performance of NiOx through reactive sputtering or directly doping NiOx targets with metal ions, both of which incur high costs and low efficiency, we employ an evaporation method using LiF to achieve efficient and low-cost doping of NiOx. Compared to the pristine NiOx, the incorporation of LiF significantly increases the conductivity of NiOx. Additionally, the incorporation of LiF enhances the quality of the deposited perovskite films, as well as the energy level alignment and symmetry between NiOx and the perovskite, effectively improving the hole extraction and transport capabilities between NiOx and the perovskite. As a result, the PSM (active area of 57.30 cm²) fabricated in air achieves an impressive efficiency of 19.54%. Furthermore, the unencapsulated PSM retains 80% of its initial efficiency after 700 h of continuous illumination, whereas the NiOx-based PSM drops to 80% after only 150 h. This study provides a simple and low-cost method for doping NiOx, which is of great significance for the further industrialization of PSMs.

High Efficiency n-Type Doping of Organic Semiconductors by Cation Exchange.

Achieving efficient doping in n-type conjugated polymers is crucial for their application in electronic devices. In this study, an n-type doping method is developed based on cation exchange that maintains a high doping level while ensuring a high degree of structural order, leading to significantly improved electrical conductivity. By investigating various dopants and ionic liquids, it is discovered that the choice of dopant influences doping efficiency, while the selection of ionic liquid affects cation exchange efficiency. Through careful selection of suitable dopants and ionic liquids, High doping levels are achieved remarkably in a short period, resulting in the highest conductivity (nearly 1×10- 2Scm-¹) compared to other doping methods for poly{[N,N'-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5'-(2,2'-bithiophene)} (N2200). The findings highlight the robustness and efficiency of cation exchange doping as an effective approach for achieving high-quality n-type doping in conjugated polymers, thereby opening new avenues for the development of advanced polymer-based electronic devices.

The performance prediction and mechanism study of doped DLC films by the combination of molecular dynamics and first-principles calculations

Doped DLC film is expected to be a vital surface protection material in aerospace and other important fields. However, the long experiment cycle for screening efficient dopants, premature failure caused by high residual stress, and insufficient understanding of the microscopic mechanism, seriously limit its further improvement. In this work, the performance prediction and mechanism study of doped DLC films were proposed by combining molecular dynamics (MD) and first-principles calculations, and the commonly used Si and MoS2 were selected as the typical elemental and compound dopants for investigations, respectively. MD was used to evaluate the influence of both the type of dopant and its amount on the structure and properties, including the content of sp2-C and sp3-C, hardness, elastic modulus, and friction coefficient of DLC films. First-principles calculations were performed to study the modification mechanism of Si and MoS2 dopants from a viewpoint beyond the experimental scale. This study was verified by experimental investigation and proven to make a fast prediction and screening for the doping craft of DLC films.

Coordination Structure Modulation in Group-VIB Metal Doped Ag3PO4 Augments Active Site Density for Electrocatalytic Conversion of N2 to NH3.

Doping is considered a promising material engineering strategy in electrochemical nitrogen reduction reaction (NRR), provided the role of the active site is rightly identified. This work concerns the doping of group VIB metal in Ag3PO4 to enhance the active site density, accompanied by d-p orbital mixing at the active site/N2 interface. Doping induces compressive strain in the Ag3PO4 lattice and inherently accompanies vacancy generation, the latter is quantified with positron annihilation lifetime studies (PALS). This eventually alters the metal d-electronic states relative to Fermi level and manipulate the active sites for NRR resulting into side-on N2 adsorption at the interface. The charge density deployment reveals Mo as the most efficient dopant, attaining a minimum NRR overpotential, as confirmed by the detailed kinetic study with the rotating ring disk electrode (RRDE) technique. In fact, the Pt ring of RRDE fails to detect N2H4, which is formed as a stable intermediate on the electrode surface, as identified from in-situ attenuated total reflectance-infrared (ATR-IR) spectroscopy. This advocates the complete conversion of N2 to NH3 on Mo/Ag3PO4-10 and the so-formed oxygen vacancies formed during doping act as proton scavengers suppressing hydrogen evolution reaction resulting into a Faradaic efficiency of 54.8% for NRR.

Inter‐Ion Mutual Repulsion Control for Nonvolatile Artificial Synapse

AbstractOrganic electrochemical transistors (OECTs) are promising candidates for artificial synapses to achieve high‐performance synaptic characteristics. While most research has focused on modifying the properties of organic semiconductors for efficient ion doping, there is a lack of systematic investigation into the relationship between ion‐mediated mechanisms and synaptic performance. In this study, an effective strategy for enhancing electrochemical doping and de‐doping by utilizing different coulombic anions is proposed. The findings reveal that doped ions in the channel layer affect inter‐ion interactions, influencing the non‐volatile effects by improving the doping performance of the synaptic device. Moreover, electrochemical analysis indicates that ions in the channel layer are sequentially de‐doped, enabling high linearity and symmetry. The fabricated devices demonstrate high‐performance synaptic properties including a retention time of ≈102 s with ≈50% retention over peak current and near‐ideal long‐term potentiation/long‐term depression (LTP/LTD) through effective electrochemical doping and de‐doping. These results show that controlling both the properties of organic semiconductors and ion interactions in the electrolyte is crucial for OECTs, opening up various applications for neuromorphic computing.

The critical role of energetic fluctuations in charge separation for efficient molecular doping of organic semiconductors

The critical role of energetic fluctuations in charge separation for efficient molecular doping of organic semiconductors

Nanotechnology in the sports athlete community based on its application in doping detection: a systematic literature review and meta-analysis

This study examines the effectiveness and accuracy of nanotechnology applications in doping detection within the athlete community. Nanotechnology offers a novel approach with potential in detecting doping substances more efficiently and accurately. The method used in this study is a Systematic Literature Review (SLR) and meta-analysis, with articles selected from the Scopus and Web of Science (WoS) databases covering the years 2020-2024. The selection process employs the PRISMA method and includes only research articles relevant to the topic. A total of 13 studies were selected for further analysis. The meta-analysis results indicate that the Differential Pulse Voltammetry (DPV) and Enzyme-Linked Immunosorbent Assay (ELISA) methods provide highly accurate and reliable results in doping detection. No significant differences were found between the use of serum and urine as test samples. Additionally, nanocomposite sensors proved to be more effective than regular sensors in detecting doping substances with high accuracy. Key findings from the results include no significant effect distinguishing between the DPV and ELISA methods (Z = 0.53, P = 0.60), no significant heterogeneity among the studies analyzed concerning serum and urine (Chi² = 0.90, df = 2, P = 0.64; Tau² = 0.00), and nanocomposite sensors proving to be more effective than regular sensors (Z = 4.14, P < 0.0001; I² = 0%). In conclusion, nanotechnology has great potential to enhance doping detection in sports. The use of nanomaterials and nanosensors can improve the sensitivity, specificity, and accuracy in detecting doping substances, making it a highly effective tool for maintaining the integrity and health of athletes. This study provides a strong foundation for the development of more efficient and effective nanotechnology-based doping detection technologies in the future. Keywords: Nanotechnology, doping, sensors, sports, athletes.

The Doping Strategies for Modulation of Transport Properties in Thermoelectric Materials

AbstractDoping is a key method employed in semiconductor technology for tuning the carrier‐density‐dependent electrical properties. In thermoelectric materials, which are typically heavily doped semiconductors, more impact factors are needed to be considered due to the heavy dose doping compared to normal semiconductors beyond carrier concentration optimization, such as band structure modification, carrier scattering mechanism and even thermal transport property. In this review, the doping effect determined by the intrinsic band features and vice versa the influence of dopants on band structure is first illustrated; and then introduce the approaches to overcoming the dilemma in effective doping caused by the temperature‐dependent optimal carrier concentration. Second, the strategies including rational vacancy design, proper selection of dopants and lattice purification toward high efficient doping and weakened carrier scattering strength are reviewed. Third, the recent discovery of the effect of dopant on thermal transport is highlighted covering the dopant‐induced local lattice distortion and exceptional strong electron‐phonon coupling. Finally, a perspective is given for the doping strategies to further boost the performance of thermoelectric materials.

Efficient doping of Spiro-OMeTAD by NO2

Doping of 2,2′,7,7′-tetrakis(N,N-di-4-methoxyphenylamino)-9,9′-spirobifluorene(Spiro-OMeTAD), which is the most common used hole transport material in perovskite solar cells, is widely studied. Especially, bis(trifluoromethane)sulfonamide (Li-TFSI) combined with 4-tert-butylpyridine (TBP) is the most studied dopant to improve the conductivity of Spiro-OMeTAD, with conductivity around 6×10−8 S/cm. In this study, we employed a new oxidizing agent NO2 to dop the Spiro-OMeTAD simply by vapor exposure, showing efficient doping with conductivity up to 2.53×10−3 S/cm and excellent film quality. The doping mechanism was further analyzed by ultraviolet-visible-near infrared spectroscopy (UV-Vis-NIR), electron paramagnetic resonance spectroscopy (EPR), Fourier infrared absorption spectroscopy (TFIR), and X-ray photoelectron spectroscopy. Our findings highlight the potential of molecular doping with NO2 to significantly improve the conductivity of Spiro-OMeTAD, providing a deep understanding of the doping effects on Spiro-OMeTAD.

Efficient Charge Transfer in Graphene/CrOCl Heterostructures by van der Waals Interfacial Coupling.

Due to the large volume of exposed atoms and electrons at the surface of two-dimensional materials, interfacial charge coupling has been proven as an efficient strategy to engineer the electronic structures of two-dimensional materials assembled in van der Waals heterostructures. Recently, heterostructures formed by graphene stacked with CrOCl have demonstrated intriguing quantum states, including a distorted quantum Hall phase in the monolayer graphene and the unconventional correlated insulator in the bilayer graphene. Yet, the understanding of the interlayer charge coupling in the heterostructure remains challenging. Here, we demonstrate clear evidences of efficient hole doping in the interfacial-coupled graphene/CrOCl heterostructure by detailed Raman spectroscopy and electrical transport measurements. The observation of significant blue shifts and stiffness of graphene Raman modes quantitatively determines the concentration of hole injection of about 1.2 × 1013 cm-2 from CrOCl to graphene, which is highly consistent with the enhanced conductivity of graphene. First-principles calculations based on density functional theory reveal that due to the large work function difference and the electronegativity of Cl atoms in CrOCl, the electrons are efficiently transferred from graphene to CrOCl, leading to hole doping in graphene. Our findings provide clues for understanding the exotic physical properties of graphene/CrOCl heterostructures, paving the way for further engineering of quantum electronic states by efficient interfacial charge coupling in van der Waals heterostructures.

Novel Ni/ZnO Nanocomposites for the Effective Photocatalytic Degradation of Malachite Green Dye

Water scarcity threatens human civilization because of rapid industrialization's damage to freshwater sources. Pollutants like dyes, which are frequently found in the paper, leather, food, plastics, textile, and cosmetics industries, must be removed to preserve water. In the present study, Zinc oxide nanocomposites impregnated with nickel (Ni/ZnO) were prepared using a wet impregnation technique. These novel materials were investigated for their ability to photocatalytically degrade malachite green (MG) under the irradiation of visible. The synthesized nanocomposite catalyst was characterized by various analytical techniques, including SEM, EDX, XRD, and BET methods of surface analysis, and revealed a high surface area of 192.88 m2g-1 with an average size range from 88-354 nm. EDX results showed efficient doping of Ni (28.9%). The composites were then used under the influence of a visible light source to degrade MG dye. The investigation also assessed the degradation of MG using a photo-Fenton reagent. Factors such as catalyst dosage, H2O2 levels, pH, and duration were optimized to understand their impact in both degradation studies. The synthesized catalyst showed stunning photocatalytic activities, as 99.4% of the 60 µg.ml-1of MG was degraded in 40 min with 100 mg of Ni/ZnO at pH 8. Ni/ZnO had a good application prospect for MG degrading and can be used as a potential photocatalyst. Doi: 10.28991/CEJ-2024-010-08-011 Full Text: PDF

Doping strategies for β-Ga2O3 based on high-throughput first-principles calculations

β-Ga2O3 is a promising material for advanced optoelectronic semiconductors due to its wide bandgap and high breakdown voltage. However, achieving efficient p-type doping remains a challenge. This investigation employs high-throughput (HT) first-principles calculations to explore doping effects in β-Ga2O3 systematically. The results of HT first-principles calculations indicate that changes in the Fermi levels (EF) can reflect the type of dopant elements. We systematically evaluated nine candidate dopants using GGA+U calculations. Through analysis of the (0/−1) transition levels, the ability to form shallow acceptors gradually decreases in the order of Zn, Mg, Cu, Hg, and Ag. Interestingly, due to the GGA+U optimization process considering electron correlation and localization effects, Mg-doped β-Ga2O3 exhibits an impurity level near the conduction band minimum (CBM), contributed by Mg2p and O2p orbitals. Mulliken population analysis reveals that Cu exhibits the highest charge density after doping compared to Hg, Zn, and Mg. Additionally, Ag-doped β-Ga2O3 shows potential for UV device applications within the 200 nm to 280 nm spectrum. The insights from this study delineate effective p-type doping strategies for β-Ga2O3, contributing to the advancement of optoelectronic device development involving semiconductors.

Enhanced p-type conductivity of hexagonal boron nitride by an efficient two-step doping strategy

The present study proposes a two-step doping strategy for achieving efficient Mg doping of h-BN, involving an additional post-annealing treatment. This approach leads to ∼108-fold enhancement in conductivity of h-BN, compared with the as-doped h-BN grown by low-pressure chemical vapor deposition. The mechanism for large enhancement in h-BN doping efficiency after post-annealing was investigated, providing evidence that this treatment not only facilitates the nanoparticle decomposition and incorporation of Mg atoms into h-BN, but also restores its lattice defects. The efficient two-step doping strategy for p-type h-BN in this study enlightens its promising prospects for ultraviolet optoelectronic devices.

Defect Engineering of MoTe2 via Thiol Treatment for Type III van der Waals Heterojunction Phototransistor.

Molybdenum ditelluride (MoTe2) nanosheets have displayed intriguing physicochemical properties and opto-electric characteristics as a result of their tunable and small band gap (Eg ∼ 1 eV), facilitating concurrent electron and hole transport. Despite the numerous efforts devoted to the development of p-type MoTe2 field-effect transistors (FETs), the presence of tellurium (Te) point vacancies has caused serious reliability issues. Here, we overcome this major limitation by treating the MoTe2 surface with thiolated molecules to heal Te vacancies. Comprehensive materials and electrical characterizations provided unambiguous evidence for the efficient chemisorption of butanethiol. Our thiol-treated MoTe2 FET exhibited a 10-fold increase in hole current and a positive threshold voltage shift of 25 V, indicative of efficient hole carrier doping. We demonstrated that our powerful molecular engineering strategy can be extended to the controlled formation of van der Waals heterostructures by developing an n-SnS2/thiol-MoTe2 junction FET (thiol-JFET). Notably, the thiol-JFET exhibited a significant negative photoresponse with a responsivity of 50 A W-1 and a fast response time of 80 ms based on band-to-band tunneling. More interestingly, the thiol-JFET displayed a gate tunable trimodal photodetection comprising two photoactive modes (positive and negative photoresponse) and one photoinactive mode. These findings underscore the potential of molecular engineering approaches in enhancing the performance and functionality of MoTe2-based nanodevices as key components in advanced 2D-based optoelectronics.

Nitrogen-doped biochar derived from corn straw for CO2 adsorption: a new vision on nitrogen sources comparison

Biochar as a highly promising CO2 adsorbent is of great significance in addressing global warming and promoting human health. Research has shown that nitrogen doping improves the CO2 adsorption performance of biochar, but selecting chemical nitrogen sources such as urea and melamine to prepare nitrogen-doped biochar is not conducive to green production and environmental protection. Therefore, it is necessary to identify a new nitrogen source to enhance the emission reduction characteristics of this process. This study selected corn straw as the raw material and cow manure as a representative protein-based nitrogen source to explore its potential as a urea substitute and reveal the hydrothermal carbonization doping mechanism of different nitrogen sources. The results indicated that in raw materials with the same C/N ratio, biochar prepared from cow manure as the nitrogen source had a better doping effect and CO2 adsorption performance. Moreover, a moderate amount of cow manure was beneficial for efficient nitrogen doping and the adsorption of CO2 by biochar, with a maximum CO2 adsorption performance improvement of 32.7%. Due to the different carbon-nitrogen bonds of the different nitrogen sources, urea was more likely to retain amino groups, while macromolecular protein nitrogen sources tended to retain structural nitrogen. The results of this study provide new ideas and theoretical support for preparing other nitrogen-doped carbon materials derived from biomass.Graphical

Influence of N2 plasma treatment on properties of black phosphorus devices in space electronic systems

In order to improve the country’s comprehensive national strength and seize space resources, the implementation of new space systems requires the use of advanced technology in key applications of microelectronics. To further improve device performance, black phosphorus (BP) is used to overcome feature size limitations for its atomic thickness. BP has excellent physical properties such as in-plane anisotropy, thickness-dependent direct band gap and high carrier mobility. However, the performance control of phosphene is a major challenge in practical applications. In order to tune the BP performance, various theoretical and experimental studies on the doping mechanism and strategies of BP have been proposed and reported. In this work, the performance of BP can be effectively tuned by N2 plasma treatment. By changing the power and processing time, the on-state current and mobility of the device can be effectively improved. This simple and efficient doping technique provides a valuable way to realize high performance BP thin film transistors.

N-doped β-Ga2O3/Si-doped β-Ga2O3 linearly-graded p-n junction by a one-step integrated approach

The p-n junction is the foundation building structure for manufacturing various electronic and optoelectronic devices. Ultrawide bandgap semiconductors are expected to overcome the limited power capability of Si-based electronic device, however, it is very difficult to achieve efficient bipolar doping due to the asymmetric doping effect, thereby impeding the development of p-n homojunction and related bipolar devices, especially for the Ga2O3-based materials and devices. Here, we demonstrate a unique one-step integrated growth of p-type N-doped (2¯01) β-Ga2O3/n-type Si-doped (2¯01) β-Ga2O3 films by phase transition and in-situ pre-doping of dopants, and fabrication of full β-Ga2O3 linearly-graded p-n homojunction diode from them. The full β-Ga2O3 p-n homojunction diode possesses a large built-in potential of 4.52 eV, a high operation electric field > 2.90 MV/cm in the reverse-bias regime, good longtime-stable rectifying behaviors with a rectification ratio of 104, and a high-speed switching and good surge robustness with a weak minority-carrier charge storage. Our work opens the way to the fabrication of Ga2O3-based p-n homojunction, lays the foundation for full β-Ga2O3-based bipolar devices, and paves the way for the novel fabrication of p-n homojunction for wide-bandgap oxides.