Efficient Doping Research Articles

Effect of electronic structure modulation and layer spacing change of NiAl layered double hydroxide nanoflowers caused by cobalt doping on supercapacitor performance

Layered double hydroxides (LDHs) with high theoretical capacity have broad prospectsin energy storage applications. However, their slow charge transfer kinetics and easy agglomerate hinder their applications in high-performance supercapacitors. Herein, Co2+-doped nickel aluminum layered double hydroxides (NiAl-LDH-Co2+-x, x=0, 0.3, 0.6, 0.9, 1.2, 1.5) have been designed and prepared by a convenient hydrothermal process. The multicomponent layer structure formed by cobalt doping facilitates sufficient penetration of the electrolyte and accelerates the charge transfer kinetics. Furthermore, the more open layer spacing and electronic interactions induced by Co2+ doping are conducive to accelerating ion de-intercalation, thereby further improving the kinetic behavior of charge storage. Benefiting from the unique microstructure and Co2+ doping effect, the prepared NiAl-LDH-Co2+-0.9 provides a superior specific capacity of 985 C g-1 at 1 A g-1. In addition, the assembled hybrid supercapacitor with the NiAl-LDH-Co2+-0.9 as the positive electrode provides a remarkable energy density of 22.51 Wh kg-1 at a power density of 800Wkg-1 and exhibits an excellent cycle life with 80% capacity retention after 20,000 cycles. This study demonstrates the great potential of efficient microstructure design and doping strategy in enhancing the charge storage of electrode materials.

Unlocking the effect of Li and Ce ions on the thermoluminescence and optically stimulated luminescence signals of the MgB4O7 compound.

Magnesium tetraborate (MgB4O7) is an example of a material that has attracted the attention of researchers in the field of ionising radiation dosimetry. Several challenges are present in order to achieve considerable advances in luminescence dosimetry. The incorporation of efficient dopants in the host matrix has been an experimentally useful but limited strategy. The lack of specific information about the introduced defects as well as their connection with the trapping and recombination processes associated with light emission may be quoted as challenging examples. Here, we demonstrate the influence of lithium incorporation on Optically Stimulated Luminescence (OSL)/Thermoluminescence (TL) signal modification/suppression of MgB4O7 by combining experimental and computational procedures. Li substitution into the Mg site leads to a signal suppression due to the probable quenching of the Fs and Fs+ centres in MgO and the formation of O''i, drastically reducing the possibility of MgO anti-Schottky defect formation in MgB4O7. When using Li-co-doped MgB4O7:Ce3+, the Li ions act as a charge balancer, facilitating the entry of Ce ions into the interstitial pores and making possible a positive synergistic effect on the luminescence and dosimetric properties. These findings provide new insights into designing more efficient dosimeters by tuning dopants.

Electron transfer driving force as the criterion for efficient n-doping of organic semiconductors with DMBI-H derivatives

The electron affinity (EA) of OSCs and the ionization energy (IE) of dopant radicals (D˙s) are two molecular descriptors for the n-doping reaction with DMBI-H derivatives, and EA(OSC) − IE(D·) > 1.0 eV is proposed as a criterion for efficient doping.

Theoretical prediction of two-element two-dimensional layered structures and efficient doping engineering on carbon phosphide

We discovered three new novel stable two-dimensional (2D) materials that have not been reported before by replacing the C or P element of the carbon phosphide (CP) monolayer entirely.

Efficient doping to synthesize high-performance Co/Fe-BiOCl photocatalyst assisted by the ion release from novel CoFe2O4 nanofiber reservoir

Metal ion doping is an efficient method to achieve high photocatalytic performance of semiconductors. However, the current synthetic methods by using inorganic salts as doped sources in the precursor reaction system might suffer from ion waste and second pollution. Herein, we developed a novel method by employing electrospun nanofibers as ion reservoir to release metal ions for the synthesis of ion-doped semiconductors with high photocatalytic activity. As demonstrated, Co/Fe co-doped BiOCl photocatalyst (Co/Fe-BOC) was facilely prepared in the presence of CoFe2O4 nanofibers as Co and Fe ion reservoir via a simple solvothermal method. Compared with BiOCl, the resulted Co/Fe-BOC shows increased specific surface area, visible light response as well as separation and transportation efficiencies of photogenerated carriers. Thus, the Co/Fe-BOC exhibits significantly enhanced visible light photocatalytic activity to degrade 99.4% rhodamine B (RhB) within 4 min. This new doping approach not only avoids the ion waste and pollution during the reaction process but also facilitates the separation of the photocatalyst. Moreover, the CoFe2O4 nanofibers could be repeatedly used as ion reservoir to prepare high-performance Co/Fe-BOC. This nanofiber-based ion doping approach provides a novel, universal and promising insight to obtain doped semiconductors with high photocatalytic activity.

Development of Sulfur-Doped Graphitic Carbon Nitride for Hydrogen Evolution under Visible-Light Irradiation.

Developing eco-friendly strategies to produce green fuel has attracted continuous and extensive attention. In this study, a novel gas-templating method was developed to prepare 2D porous S-doped g-C3N4 photocatalyst through simultaneous pyrolysis of urea (main g-C3N4 precursor) and ammonium sulfate (sulfur source and structure promoter). Different content of ammonium sulfate was examined to find the optimal synthesis conditions and to investigate the property-governed activity. The physicochemical properties of the obtained photocatalysts were analyzed by X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), scanning transmission electron microscopy (STEM), specific surface area (BET) measurement, ultraviolet-visible light diffuse reflectance spectroscopy (UV/vis DRS), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) spectroscopy and reversed double-beam photo-acoustic spectroscopy (RDB-PAS). The as-prepared S-doped g-C3N4 photocatalysts were applied for photocatalytic H2 evolution under vis irradiation. The condition-dependent activity was probed to achieve the best photocatalytic performance. It was demonstrated that ammonium sulfate played a crucial role to achieve concurrently 2D morphology, controlled nanostructure, and S-doping of g-C3N4 in a one-pot process. The 2D nanoporous S-doped g-C3N4 of crumpled lamellar-like structure with large specific surface area (73.8 m2 g-1) and improved electron-hole separation showed a remarkable H2 generation rate, which was almost one order in magnitude higher than that of pristine g-C3N4. It has been found that though all properties are crucial for the overall photocatalytic performance, efficient doping is probably a key factor for high photocatalytic activity. Moreover, the photocatalysts exhibit significant stability during recycling. Accordingly, a significant potential of S-doped g-C3N4 has been revealed for practical use under natural solar radiation.

Designing Superalkali Metals-Doped Sumanene-Based Highly Efficient Nonlinear Optical Materials for Cutting-Edge Optoelectronic Applications

Nonlinear optical (NLO) materials have attracted bounteous scientific attention in the modern era because of their optoelectronic and biological applications. In this respect, an attempt is made to present thermodynamically stable superalkali metals (Li3N, Li3O, Li3S and Li3F)-doped sumanene (C[Formula: see text]H[Formula: see text])-based complexes with fine NLO response properties. Nine isomers (I–III of Li3N@Sumanene, I–II of Li3O@Sumanene, I–II of Li3S@Sumanene and I–II of Li3F@Sumanene) are proposed, and their geometric, thermodynamic, electronic and NLO properties are explored by using density functional theory (DFT) calculations. Computational results reveal that the [Formula: see text] gap is reduced up to 0.56[Formula: see text]eV for doped complexes. The maximum hyperpolarizability response is calculated [Formula: see text][Formula: see text]a.u. for isomer II of the Li3F@Sumanene series. The participation of distinct fragments, type of interaction, and charge transfer are computed by the corresponding TDOS and PDOS, NCI and NBO analysis. For UV–Vis analysis and crucial excitation state, TD-DFT calculations are carried out, which exhibits that all doped complexes are transparent in the UV region. NCI analysis confirmed the Van-der Waals interactions as an important mode of adsorption between superalkalis and sumanene. This report provides an efficient superalkali doping technique for creating highly effective future NLO systems and recommends superalkali-doped sumanene systems as ideal NLO prospects for future NLO applications.

Insights into the effects of Al-ion implantation temperature on material properties of 4H-SiC

In this study, Al implantation in 4H-SiC at the dose of 1 × 1014 cm−2 was investigated. The impacts of implantation temperature on the lattice quality, microstructure, surface composition, and band structure were all studied experimentally and theoretically. Atomic force microscope (AFM) images showed the difference in surface morphology between high-temperature and low-temperature implantation. Transmission electron microscopy (TEM) characterization indicated the lattice damage induced by implantation was recovered after the post-annealing at 1750 °C, except for the samples implanted at room temperature. X-ray photoelectron spectroscopy (XPS) analysis suggested an oxidation effect during and after the implantation process, and it was more serious at lower implantation temperatures. As the implantation temperature incremented, the ratio of Si-C composition with high binding energy increased, the element valence became closer to that of ideal Al-doped 4H-SiC calculated by density functional theory (DFT); and the Fermi level shifted toward the valence band maximum (VBM), demonstrating the formation of efficient p-type doping. A more obvious asymmetric broadening in Raman spectroscopy was observed at higher implantation temperature. The theoretically obtained band structures and bond lengths from DFT calculations corroborated the experimental results, providing physical insights into the possible effect mechanism. In sum, correlations between the implantation process, external material properties, and internal crystal structure were recorded, paving the way for further research and future applications.

Femtosecond nonlinear optical response and minority carrier lifetime of F4TCNQ-doped bismuthene for optoelectronic and ultrafast photonic applications

Bismuthene has received a lot of interest because of its unusual electronic and photonic properties. To widen the use of bismuthene in optoelectronic and ultrafast photonic devices, its electronic and optical characteristics should be tuned. Herein, for the first time, a strong p-type molecular dopant, such as tetrafluoro-tetracyanoquinodimethane (F4TCNQ), is used to achieve efficient surface charge transfer doping (SCTD) of bismuthene. The minority carrier lifetime measurements of bismuthene shifted to 6.5 µs after doping, confirming that F4TCNQ has the opportunity to boost bismuthene's p-type conductivity due to an unusual charge transfer interaction between bismuthene and F4TCNQ molecules. The thermally generated intermolecular charge transfer influence between bismuthene and F4TCNQ resulted in an improved nonlinear optical and optical limiting response, which was estimated by femtosecond z-scan measurements. Our findings suggest that SCTD is an appropriate means for tuning the linear and nonlinear optical properties of bismuthene via modulating their band gap and minority carrier lifetime. This alternating approach expands its potential in electronic, optoelectronic, and ultrafast photonic devices.

A "Click" Reaction to Engineer MoS2 Field-Effect Transistors with Low Contact Resistance.

Two-dimensional (2D) materials with the atomically thin thickness have attracted great interest in the post-Moore's Law era because of their tremendous potential to continue transistor downscaling and offered advances in device performance at the atomic limit. However, the metal-semiconductor contact is the bottleneck in field-effect transistors (FETs) integrating 2D semiconductors as channel materials. A robust and tunable doping method at the source and drain region of 2D transistors to minimize the contact resistance is highly sought after. Here we report a stable carrier doping method via the mild covalent grafting of maleimides on the surface of 2D transition metal dichalcogenides. The chemisorbed interaction contributes to the efficient carrier doping without degrading the high-performance carrier transport. Density functional theory results further illustrate that the molecular functionalization leads to the mild hybridization and the negligible impact on the conduction bands of monolayer MoS2, avoiding the random scattering from the dopants. Differently from reported molecular treatments, our strategy displays high thermal stability (above 300 °C) and it is compatible with micro/nano processing technology. The contact resistance of MoS2 FETs can be greatly reduced by ∼12 times after molecular functionalization. The Schottky barrier of 44 meV is achieved on monolayer MoS2 FETs, demonstrating efficient charge injection between metal and 2D semiconductor. The mild covalent functionalization of molecules on 2D semiconductors represents a powerful strategy to perform the carrier doping and the device optimization.

Highly efficient two-step nitrogen doping of graphene oxide-based materials in oxygen presence atmosphere for high-performance transistors and electrochemical applications

Nitrogen content in graphene influences application performance. Although many studies have been conducted on single-process nitrogen (N)-doping, dopant content is still quite low. Therefore, the objective of this study was to develop a novel two-step economical doping technique for improved nitrogen content and device performance. First, graphene oxide (GO) was hydrothermally nitrogen-doped. This nitrogen-doped reduced graphene oxide (NrGO) was then subjected to secondary plasma treatment. Two nitrogen(N)-doping mechanisms were observed depending on graphene’s oxygen functionalized group (OFG) content. OFG assisted N-doping mechanism was dominant if graphene had a high OFG content. Despite the presence of oxygen in plasma, significant OFG reduction and a higher degree of N-doping were observed. On the other hand, if graphene had a low OFG content, activated radicals in graphene structure by plasma ion bombardment mainly influenced secondary N-doping. Here, oxygen contaminants in the plasma stream showed dual effects. Low-power conditions showing no significant effect, whereas high-power plasma influenced re-oxidation and suppressed further N-doping. The maximum N/C ratio of 0.168 was observed in 5 W plasma-treated NrGO material which had nitrogen content over 40%. Compared to a single-step N-doping technique, this new technique can facilitate dominant n-type transistors with strong oxygen reduction characteristics. • The impact of oxygen in plasma depends on OFGs in graphene and plasma power. • Oxygen contaminants can suppress N-doping if graphene has low OFG content. • Oxidized nitrogen formation has no impact by oxygen contaminants in plasma. • Two-step N-doping can provide high N-doping level than single-step doping.

Improving excitons utilization of blue thermally activated delayed fluorescence emitter to achieve highly efficient solution-processed hybrid white organic light-emitting diodes

5-(5,9-dioxa-13b-boranaphtho[3,2,1-de]anthracen-7-yl)-10,15-diphenyl-10,15-dihydro-5H-diindolo[3,2-a:3′,2′-c]carbazole (DBA-DI) with high triplet energy was utilized as efficient blue emission dopant to construct solution-processed thermally activated delayed fluorescence-phosphorescence (TADF-phosphorescence) hybrid white organic light-emitting diodes (WOLEDs). Meanwhile, a series of TADF-phosphorescence hybrid WOLEDs composed of bis(2-phenylquinoline) (2,2,6,6-tetramethylheptane-3,5-dionate)iridium(III) (PQ2Ir(dpm)), tris(2-(4-tolyl)-phenylpyridine)iridium (Ir(mppy)3) and DBA-DI are successfully developed by introducing the co-host system consist of poly(N-vinylcarbazole) (PVK) and 2,6-bis(3-(9H-carbazol-9-yl)phenyl)pyridine (26DCzPPy) with high color rendering index (CRI) and improving the utilization of triplet excitons. Furthermore, energy transfer processes among different emitters were investigated in detail based on absorbance spectra, photoluminescence and transient photoluminescence spectra. Ultimately, the Commission Internationale de I'Eclairage coordinates of the optimum solution-processed WOLEDs in warm-white emission region are (0.41, 0.41) and high CRI is 82. Furthermore, the same device realized outstanding efficiencies of 32.14 cd A−1, 21.00 lm W−1 and 15.1% at high brightness of 1000 cd m−2.

Enhanced thermoelectric performance in n-type Mg3.2Sb1.5Bi0.5 doping with lanthanides at the Mg site

• Gd and Ho have increased the DOS of the valence band near the Fermi level, and the d electrons of Gd and Ho have made extraordinary contributions. • Gd and Ho are effective n-type cation site dopants with higher doping efficiency and better carrier concentration than the anion site dopants chalcogenide elements. • For Mg 3.2 Gd 0.02 Sb 1.5 Bi 0.5 and Mg 3.2 Ho 0.02 Sb 1.5 Bi 0.5 samples, we obtain high zT values of 1.61 and 1.55 at 725 K, respectively. • Gd as well as Ho are an alternative effective n-type doping element for higher thermoelectric performance. Mg-based thermoelectric materials have attracted more and more attention because of their rich composition elements, green environmental protection, and lower price. In recent years, the thermoelectric properties of n-type Mg 3 Sb 2 materials have been optimized by doping chalcogenide elements (S, Se, and Te) at the anionic position. In this work, n-type Mg 3.2 A x Sb 1.5 Bi 0.5 ( A = Gd, Ho; x = 0.01, 0.02, 0.03, and 0.4) samples were prepared by the cation site doping of lanthanide elements (Gd and Ho). The research results show that Gd and Ho doped n-type Mg 3.2 Sb 1.5 Bi 0.5 samples are entirely comparable to the S, Se, and Te doped n-type Mg 3.2 Sb 1.5 Bi 0.5 samples, demonstrating more excellent thermoelectric properties. Doping with lanthanides (Gd and Ho) at the Mg site increases the carrier concentration of the material to 8.161 × 10 19 cm −3 . Doping induces the contribution of more electron, thus obtaining higher conductivity. The maximum zT value of the Mg 3.2 Gd 0.02 Sb 1.5 Bi 0.5 and the Mg 3.2 Ho 0.02 Sb 1.5 Bi 0.5 samples reaches 1.61 and 1.55, respectively. This work theoretically and experimentally demonstrates Gd and Ho are efficient n-type dopants for Mg 3.2 Sb 1.5 Bi 0.5 thermoelectric material.

Tuning the p-type doping of GaN over three orders of magnitude via efficient Mg doping during halide vapor phase epitaxy

The precise control of Mg concentration ([Mg]) in p-type GaN layers from 2.3 × 1016 to 2.0 × 1019 cm−3 was demonstrated by halide vapor phase epitaxy (HVPE) on n-type GaN (0001) freestanding substrates. [Mg] in GaN layers could be controlled well by varying the input partial pressure of MgCl2 formed by a chemical reaction between MgO solid and HCl gas under the thermodynamic equilibrium condition. In the sample with [Mg] of 2.0 × 1019 cm−3, a step-bunched surface was observed because the surface migration of Ga adatoms was enhanced by the surfactant effect of Mg atoms. The samples show high structural qualities determined from x-ray rocking curve measurements. The acceptor concentration was in good agreement with [Mg], indicating that almost all Mg atoms act as acceptors. The compensating donor concentrations in the samples were higher than the concentrations of Si, O, and C impurities. We also obtained the Mg acceptor level at a sufficiently low net acceptor concentration of 245 ± 2 meV. These results show that the HVPE method is promising for fabricating GaN vertical power devices, such as n-channel metal–oxide–semiconductor field-effect transistors.

Tailorable Electronic and Electric Properties of Graphene with Selective Decoration of Silver Nanoparticles by Laser-Assisted Photoreduction.

While graphene shows great potential for diverse device applications, to broaden the scope of graphene-based device applications further, it would be necessary to tune the electronic state of graphene and its resultant electrical properties properly. Surface decoration with metal nanoparticles is one of the efficient doping methods to control the properties of two-dimensional materials. Here, we report the p-type doping effects in single-layer graphene decorated with silver nanoparticles (AgNPs) that were formed area-selectively by the facile one-step photoreduction (PR) process based on focused-laser irradiation. During the PR process, AgNPs were reduced on graphene in AgNO3 solution by laser-driven photoexcitation followed by chemical reactions. Based on scanning electron microscopy analyses, the morphology characteristics of AgNPs were shown to be modulated by the laser dwell time and power controllably. Further, p-type doping effects were demonstrated using graphene-field-effect transistor structures whose graphene channels were selectively decorated with AgNPs by the PR process, as validated by the decrease in channel resistance and the shift of the Dirac point voltage. Moreover, the growth of AgNPs was observed to be more active on the graphene channel that was laser-annealed ahead of the PR process, leading to enhancing the efficiency of this approach for altering device characteristics.

Charge Transfer Doping of Carbon Nitride Films through Noncovalent Iodination for Enhanced Photoelectrochemical Performance: Combined Experimental and Computational Insights.

To improve the photoelectrochemical (PEC) performance of photocatalysts, the doping strategy through covalent functionalization is often adopted to adjust material electronic structures. By contrast, this work demonstrates that the noncovalent interaction in the case of iodinated graphitic carbon nitride (g-CN) film can also enhance the PEC performance. Through a facile synthesis method of rapid thermal vapor condensation (RTVC), the preparediodinated g-CN film shows a significantly improved photocurrent density (38.9µAcm-2 ), three times that of pure g-CN film (13.0µAcm-2 ) at 1.23V versus reversible hydrogen electrode. Computations reveal that the noncovalent attachment of iodine anion (I- ) on g-CN plays a crucial role in modulating the bandgap states and broadening of the visible-light absorption range as well as the charge carrier separation with the photo-induced hole confined to I- and electron to g-CN film. The fully filled valence orbitals (4d10 5s2 5p6 ) of I- determine its noncovalent attachment on the g-CN film and so do the iodine species of I3 - , I5 - , etc. This work offers a favorable synthesis method to achieve efficient doping through noncovalent charge transfer between thin film and certain dopants and provides a useful modification strategy for the establishment of multi-channel transportation of charge carriers in general photocatalysts.

Reassessment of silicon heterojunction cell performance under operating conditions

Temperature coefficient (TC) is a critical operational parameter for solar modules. Amorphous/crystalline silicon heterojunction (SHJ) solar cell is usually considered as a good choice for installation in hot climates because of its lowest TC amongst silicon solar cells. Recently, we have found that light soaking can activate efficient boron doping in hydrogenated amorphous silicon (a-Si:H), which improves the efficiency of SHJ solar cells by enhanced field effect passivation and declined series resistance. In this study, we further report that high temperature can boost this light-induced doping effect. This implies that SHJ solar cells can generate more electricity than estimated by indoor International Electrotechnical Commission (IEC) standards in light abundant locations with hot climates. As a consequence, a 100 MW solar plant comprising SHJ solar modules will gain an extra income of more than 2 million U.S. dollars in a 25-year operation period. Additionally, for the first time, we demonstrate that the dark conductance of phosphorus-doped a-Si:H (n-a-Si:H) increases more greatly than that of boron-doped a-Si:H (p-a-Si:H) after one-sun illumination. This finding has an important implication for bifacial solar modules.

Double reaction initiated self-assembly process fabricated hard carbon with high power capability for lithium ion capacitor anodes

Hard carbons (HCs) are an ideal anode materials for lithium ion capacitors (LICs). However, its power capability is limited by low conductivity and poor ion diffusion kinetics. Optimized graphitic degree, appropriate hierarchical pore structure and efficient heteroatom doping can enhance the rate capability from different dimensions. But it is very difficult to achieve simultaneously through simple synthetic strategies. Herein, an ingenious self-assembly strategy is presented for the preparation of N/P co-doped hierarchical porous graphitic HCs (DGPCs). In the self-assembly process, chitosan was cross-linked with Ni2+ and phytic by chelation and esterification reactions, respectively. Benefiting from the double reaction design, different active sites are separated and thus coupling of multiple modifications is achieved. Optimal sample presents excellent power performance and good cycling stability. Kinetic analysis demonstrates that the Li ion diffusion rate is effectively increased. GDPC-1//AC LIC delivered a high energy density of 50.5 Wh kg−1 at an ultra-high power density of 20 kW kg−1. The outstanding power capability is attributed to the synergistic effect between catalytic graphitization, hierarchical porous structure and N/P co-doping, which comprehensively improves the diffusion kinetics of Li+. This work provides a simple and effective strategy for realizing multiple modifications to improve the power capability of hard carbons.

Reduced dopant-induced scattering in remote charge-transfer-doped MoS2 field-effect transistors.

Efficient doping for modulating electrical properties of two-dimensional (2D) transition metal dichalcogenide (TMDC) semiconductors is essential for meeting the versatile requirements for future electronic and optoelectronic devices. Because doping of semiconductors, including TMDCs, typically involves generation of charged dopants that hinder charge transport, tackling Coulomb scattering induced by the externally introduced dopants remains a key challenge in achieving ultrahigh mobility 2D semiconductor systems. In this study, we demonstrated remote charge transfer doping by simply inserting a hexagonal boron nitride layer between MoS2 and solution-deposited n-type dopants, benzyl viologen. A quantitative analysis of temperature-dependent charge transport in remotely doped devices supports an effective suppression of the dopant-induced scattering relative to the conventional direct doping method. Our mechanistic investigation of the remote doping method promotes the charge transfer strategy as a promising method for material-level tailoring of electrical and optoelectronic devices based on TMDCs.

Boron-induced phase-transition and selenium vacancy to enhance supercapacitive performance of cobalt diselenide

The phase-transition engineering has shown great potential in designing high-performance energy storage and catalytic materials. Herein, we report the phase transition and selenium vacancy induced by the trace boron doping into CoSe2, realizing an enhancement of the performance of supercapacitor. The trace amounts of boron doping (∼ 0.07 wt%) induce the phase-transition from cubic to orthorhombic structures and trigger selenium vacancies in orthorhombic cobalt diselenide (o-CoSe2). The doped defective cobalt diselenide (o-CoSe2−x/B) exhibits a high specific capacity of 376.3 mA h g−1 at a current density of 1 A g−1, which is much larger than that of the undoped cubic cobalt diselenide (211.3 mA h g−1) and annealed cubic cobalt diselenide (208.3 mA h g−1). A hybrid supercapacitor assembled using o-CoSe2−x/B and activated carbon delivers a high energy density of 102.5 W h kg−1 at a power density of 850.4 W kg−1 and maintains an energy density of 34.0 W h kg−1 at 16,767.1 W kg−1. In addition, the device possesses an excellent cycling stability that remains 83.5 % of the initial capacitance after 25,000 cycles at a current density of 10 A g−1. These results demonstrate that the boron is a new efficient dopant that can dramatically improve the supercapacitor performance of CoSe2 through the structural phase transition and defect engineering.