P-type NiO Research Articles

The Effect of Nitrogen as a Co-Dopant in p-Type NiO:Nb Films on the Photovoltaic Performance of NiO/TiO2 Transparent Solar Cells

Doping engineering has been applied in niobium-doped NiO (NiO:Nb) by adding nitrogen (N) in its structure. The rf-sputtered films were made from a Ni-Nb composite target on unheated substrates at 300 W rf power and 5 mTorr total pressure. The plasma contained 50% Ar and 50% O2 for the fabrication of the single-doped NiO:Nb film (AΝ film), and N2 gas for the incorporation of N in the Ni-O-Nb structure. The N2 in plasma was introduced by keeping constant the flow rates of O2 and N2 gasses (O2/N2 = 1) and reducing the amount of Ar gas, namely 94% Ar, 3% O2, and 3% N2 (film AN1); 50% Ar, 25% O2, and 25% N2 (film AN2); and 6% Ar, 47% O2, and 47% N2 (film AN3). All films had the single phase of cubic NiO and both Nb and N in the Ni-O structure were revealed by XPS experiments. The roughness of the films was increased with the increase in N in plasma. Post-deposition thermal treatment improved the crystallinity and reduced the structural disorder of the films. The AN2 film was found to be the most transparent of all films, exhibiting the widest band gap, 3.72 eV, and the narrowest Urbach tail states’ width, 313 meV. The AN and the AN2 films were employed to form NiO/TiO2 heterostructures. The NiO:Nb/TiO2 and NiO:(Nb,N)/TiO2 heterostructures exhibited a visible transmittance of around 42% and 75%, respectively, and both showed rectification properties. Upon illumination with UV light, the NiO:(Nb,N)/TiO2 diode exhibited enhanced photovoltaic performance when compared to the NiO:Nb/TiO2 solar cell: the short-circuit current densities were 0.2 mA/cm2 versus 1.4 μA/cm2 and the open-circuit voltages were 0.5 V versus 0.2 V. The output characteristics of the p-NiO:(Nb,N)/n-TiO2 UV photovoltaics can be further improved by proper engineering of the individual layers and device processing procedures.

Field management in NiO x /β-Ga2O3 merged-PIN Schottky diodes: simulation studies and experimental validation

In recent years, p-type NiO x has emerged as a promising alternative to realize kilovolt-class β-Ga2O3-based PN junction diodes. However, only a handful of studies could realize β–Ga2O3-based unipolar diodes using NiO x as a guard ring or floating rings. In this work, we investigate the device design of NiO x /β-Ga2O3 unipolar diodes using the technology computer aided design simulations and experimental validations. We show that a systematic electric field management approach can potentially lead to NiO x /β-Ga2O3 heterojunction unipolar diode and offer enhanced breakdown characteristics without a severe compromise in the ON-state resistance. Accordingly, the NiO x /β-Ga2O3 heterojunction diode in the merged-PIN Schottky configuration is shown to outperform the regular Schottky diode or junction barrier Schottky diode counterpart. The analysis performed in this work is believed to be valuable in the device design of β-Ga2O3-based unipolar diodes that use a different p-type semiconductor candidate as guard rings and floating rings.

Bursting and transforming MOF into n-type ZnO and p-type NiO based heterostructure for supercapacitive energy storage

Metal-organic frameworks (MOFs) have been considered as great contender and promising electrode materials for supercapacitors. However, their low capacity, aggregation, and poor porosity have necessitated the exploration of new approaches to enhance the performance of these active materials. In this study, sphere-like MOF were in-situ grown and it subsequently burst, transformed into a desired metal oxide heterostructure comprising n-type ZnO and p-type NiO (ZnO/NiO-350). The resulting optimized flower-like structure, composed of interlaced nanoflakes derived from MOFs, greatly improved the active sites, porosity, and functionality of the electrode materials. The ZnO/NiO-350 electrode exhibited superior electrochemical activities for supercapacitors, compared to the parent MOF, bare n-type, and p-type counterparts. The specific capacitance can reach to 543 ​F ​g−1 at a current density of 1 ​A ​g−1. Theoretical modeling and simulations were employed to gain insights into the atomic-scale properties of the materials. Furthermore, an assembled hybrid device using active carbon and ZnO/NiO-350 as electrodes demonstrated excellent energy density of 44 ​Wh kg−1 at a power density of 1.6 Kw kg−1. After 5000 cycles at 10 ​A ​g−1, the cycling stability remained excellent 80 % of the initial capacitance. Overall, such evaluation of unique electrode with superior properties may be useful for the next generation supercapacitor electrode.

Drop–Dry Deposition of SnO2 Using Na2SnO3 and Fabrication of SnO2/NiO Transparent Solar Cells

In this work, SnO2 thin films are deposited by drop–dry deposition (DDD), which is a simple, low-cost chemical technique for thin film deposition. The deposition solution contains Na2SnO3 as the Sn source, and is highly stable without spontaneous reactions in the solution. The solution is dropped on a substrate heated to 60°C on a heater plate. According to Auger electron spectroscopy, the deposit will be stoichiometric SnO2. The film is n-type and transparent in the visible range. The pn heterostructure is fabricated by depositing SnO2 on p-type NiO. The NiO film is also fabricated by DDD. Ni(OH)2 is deposited using a solution containing Ni(NO3)2 and NaOH, and then is converted to NiO by annealing at 400°C. The SnO2/NiO structure is transparent in the visible range and shows clear rectification properties and photovoltaic effects. Thus, a transparent solar cell is successfully fabricated by DDD.

Inorganic hole transport layer for lead free bismuth halide perovskite for photovoltaic device

The finest Hole Transport Layer (HTL) with extraordinary optical and electrical properties are significantly influenced the Power Conversion Efficiency (PCE) of the photovoltaic device. Inorganic hole transport materials exhibit better performance than organic hole transport materials. Herein, we demonstrated that optoelectronic properties of inorganic materials of NiO doped with Cu as Hole Transport Layer (HTL) for Lead free Bismuth halide perovskite solar cell. Solution process method of sol – gel was used to synthesize p-type NiO doped with Cu and yield nano particles of high quality. Cu + doped into Ni2+ sites has improved the crystallization of nanoparticles, carrier mobility and carrier electric properties. Results of the study revealed that the Enhancement of electrical conductivity of about 2 % is obtained for NiO doped with Cu which is ∼1.287 × 10−02 compared to the pristine NiO which is ∼2.655 × 10−03.

Ga2O3/NiO junction barrier Schottky diodes with ultra-low barrier TiN contact

Power Schottky barrier diodes (SBDs) face an inherent trade-off between forward conduction loss and reverse blocking capability. This limitation becomes more severe for ultra-wide bandgap (UWBG) SBDs due to the large junction field. A high Schottky barrier is usually required to suppress the reverse leakage current at the price of an increased forward voltage drop (VF). This work demonstrates a Ga2O3 junction barrier Schottky (JBS) diode that employs the embedded p-type NiO grids to move the peak electric field away from the Schottky junction, thereby allowing for the use of an ultra-low barrier TiN Schottky contact. This JBS diode concurrently realizes a low VF of 0.91 V (at forward current of 100 A/cm2) and a high breakdown voltage over 1 kV, with the VF being the lowest in all the reported vertical UWBG power diodes. Based on the device characteristics measured up to 200 °C, we further analyze the power loss of this JBS diode across a wide range of operational duty cycles and temperatures, which is found to outperform the TiN/Ga2O3 SBDs or NiO/Ga2O3 PN diodes. These findings underscore the potential of low-barrier UWBG JBS diodes for high-frequency, high-temperature power electronics applications.

Tuning ZnO-based piezoelectric nanogenerator efficiency through n-ZnO/p-NiO bulk interfacing

ZnO based piezoelectric nanogenerators (PENG) hold immense potential for harvesting ambient vibrational mechanical energy into electrical energy, offering sustainable solutions in the field of self-powered sensors, wearable electronics, human–machine interactions etc. In this study, we have developed flexible ZnO-based PENGs by incorporating ZnO microparticles into PDMS matrix, with ZnO concentration ranging from 5 to 25 wt%. Among these, the PENG containing 15 wt% ZnO exhibited the best performance with an open-circuit output voltage/short-circuit current of ~ 42.4 V/2.4 µA. To further enhance the output performance of PENG, p-type NiO was interfaced with ZnO in a bulk hetero-junction geometry. The concentration of NiO was varied from 5 to 20 wt% with respect to ZnO and incorporated into the PDMS matrix to fabricate the PENGs. The PENG containing 10 wt% NiO exhibits the best performance with an open-circuit output voltage/short-circuit current of ~ 65 V/4.1 µA under loading conditions of 30 N and 4 Hz. The PENG exhibiting the best performance demonstrates a maximum instantaneous output power density ~ 37.9 µW/cm2 across a load resistance of 20 MΩ under loading conditions of 30 N and 4 Hz, with a power density per unit force and Hertz of about ~ 0.32 µW/cm2·N·Hz. The enhanced output performance of the PENG is attributed to the reduction in free electron concentration, which suppresses the internal screening effect of the piezopotential. To assess the practical utility of the optimized PENG, we tested the powering capability by charging various commercial capacitors and used the stored energy to illuminate 10 LEDs and to power a stopwatch displays. This work not only presents a straightforward, cost-effective, and scalable technique for enhancing the output performance of ZnO-based PENGs but also sheds light on its underlying mechanism.

Enhanced piezocatalytic and piezo-photocatalytic dye degradation via S-scheme mechanism with photodeposited nickel oxide nanoparticles on PbBiO2Br nanosheets

The fabrication of an S-scheme heterojunction demonstrates as an efficient strategy for achieving efficient charge separation and enhancing catalytic activity of piezocatalysts. In this study, a new S-scheme heterojunction was fabricated on the PbBiO2Br surface through the photo-deposition of NiO nanoparticles. It was then employed in the piezoelectric catalytic degradation of Rhodamine B (RhB). The results demonstrate that the NiO/PbBiO2Br composite exhibits efficient performance in piezocatalytic RhB degradation. The optimal sample is the NiO/PbBiO2Br synthesized after 2 h of irradiation, achieving a RhB degradation rate of 3.11 h−1, which is 12.4 times higher than that of pure PbBiO2Br. Simultaneous exposure to visible light and ultrasound further increases in the RhB degradation rate, reaching 4.60 h−1, highlighting the synergistic effect of light and piezoelectricity in the NiO/PbBiO2Br composite. A comprehensive exploration of the charge migration mechanism at the NiO/PbBiO2Br heterojunction was undertaken through electrochemical analyses, theoretical calculations, and in-situ X-ray photoelectron spectroscopy analysis. The outcomes reveal that p-type semiconductor NiO and n-type semiconductor PbBiO2Br possess matching band structures, establishing an S-scheme heterojunction structure at their interface. Under the combined effects of band bending, interface electric fields, and Coulomb attraction, electrons and holes migrate and accumulate on the conduction band of PbBiO2Br and valence band of NiO, respectively, thereby achieving effective spatial separation of charge carriers. The catalyst’s synergistic photo-piezoelectric catalysis effect can be ascribed to its role in promoting the generation and separation of charge carriers under both light irradiation and the piezoelectric field. The results of this investigation offer valuable insights into the development and production of catalytic materials that exhibit outstanding performance through the synergy of piezocatalysis and photocatalysis.

Stable and repeatable ZrO2 RRAM achieved by NiO barrier layer for negative set phenomenon elimination

Resistive random-access memory (RRAM) is a promising non-volatile memory technology due to its fast operation, low power consumption, and high reliability. However, the negative set phenomenon remains a challenge for RRAM, which can lead to the deterioration of device switching parameters. In this study, we successfully addressed this issue by inserting a NiO blocking layer between the ZrO2 and Ag top electrodes in ZrO2-based RRAM. In addition, the resistive switching characteristics of the device are significantly enhanced by the incorporation of a p-type oxide NiO layer. Compared to single-layer ZrO2 devices, the double-layer Ag/NiO/ZrO2/ITO RRAM exhibits improved cycling durability (>500 cycles) and good retention time (3 × 104s). Our analysis of the device conduction mechanism and proposed resistive switching model suggest that oxygen vacancies play a connecting role in the reset process, leading to failed reset behavior. Through the incorporation of a p-type semiconductor NiO layer into ZrO2-based RRAMs, the interference of oxygen vacancies on the reset process can be effectively impeded. This approach not only provides an effective resolution to the unforeseen negative set phenomenon in RRAM devices, but it also holds paramount significance for the advancement of high-performance RRAMs.

NO2 and NH3 detection using work function measurement of solvothermal synthesised ZnO–NiO nanocomposites: a case study

Work function measurement using Kelvin probe method has been demonstrated as an effective and novel approach towards detection of NH3 and NO2 gases using ZnO–NiO based nanocomposites. For this the nanocomposites were synthesised in different compositions using the solvothermal method. Formation of ZnO–NiO nanocomposites was confirmed using XRD and EDS studies. It is found that the nanoparticle morphology of NiO changes with different percentages of Zn addition. The work function of the sensing film was found to decrease and increase upon exposure to NH3 (1.51) and NO2 (1.18) gases owing to the reducing and oxidising nature of the test gases. Of the different composites, Zn0.75Ni0.25O exhibited highest sensor response towards the test gases. The increased response is attributed to the nanostructured morphology of the nanocomposite and the formation and collapse of the p-n heterojunction formed between p-type NiO and n-type ZnO. Besides, incorporation of NiO enhances the oxygen adsorption on the sensor surface assigned to the Ni2+ ions getting readily oxidised to Ni3+. Our results clearly suggest that the work function measurements could also be used as an effective way for NO2 and NH3 detection.

New ultrafine-flowers compositions based on Mn, Fe and Co multi-doped p-type NiO semiconductor: enhanced ferromagnetic and dielectric properties

New ultrafine-flowers compositions based on Mn, Fe and Co multi-doped p-type NiO semiconductor: enhanced ferromagnetic and dielectric properties

Correction: New ultrafine-flowers compositions based on Mn, Fe and Co multi-doped p-type NiO semiconductor: enhanced ferromagnetic and dielectric properties

Correction: New ultrafine-flowers compositions based on Mn, Fe and Co multi-doped p-type NiO semiconductor: enhanced ferromagnetic and dielectric properties

Fabrication of NiO based thin film for high-performance NO2 gas sensors at low concentrations

Recent industrial and technical developments continuously result in the release of dangerous and toxic gases that have adverse effects on human life and the environment. Metal oxide nanomaterials attract attention for extremely sensitive gas sensors owing to their high surface-to-volume ratio, thermal stability, availability, and simplicity of production. Currently, p-type NiO based gas sensors are very promising, due to their outstanding repeatability, high sensitivity, low cost, and environmentally friendly characteristics. In this work, NiO prepared by low-cost hydrothermal method and its gas sensing behavior towards NO2 gas has been studied in detail. The as-prepared structure of NiO has been analyzed by using various characterization techniques like XRD, FESEM, FTIR, BET and UV–visible absorption for the study of structural, morphological and optical properties. The NiO thin film deposited on a glass substrate was analyzed under varying concentrations of NO2 at different working temperatures (100–250 °C). The sensor demonstrated a remarkable sensitivity of 45 % to 10 ppm of NO2 at low operating temperature of 200 °C. Moreover, its consistent repeatability further underscores its reliability, emphasizing its suitability for accurate and dependable NO2 detection in diverse scenarios.

Heterojunction Devices Fabricated from Sprayed n-Type Ga2O3, Combined with Sputtered p-Type NiO and Cu2O

This work reports on the properties of heterojunctions consisting of n-type Ga2O3 layers, deposited using ultrasonic spray pyrolysis at high temperature from water-based solution, combined with p-type NiO and Cu2O counterparts, deposited by radio frequency and reactive, direct-current magnetron sputtering, respectively. After a comprehensive investigation of the properties of the single layers, the fabricated junctions on indium tin oxide (ITO)-coated glass showed high rectification, with an open circuit voltage of 940 mV for Ga2O3/Cu2O and 220 mV for Ga2O3/NiO under simulated solar illumination. This demonstrates in praxis the favorable band alignment between the sprayed Ga2O3 and Cu2O, with small conduction band offset, and the large offsets anticipated for both energy bands in the case of Ga2O3/NiO. Large differences in the ideality factors between the two types of heterojunctions were observed, suggestive of distinctive properties of the heterointerface. Further, it is shown that the interface between the high-temperature-deposited Ga2O3 and the ITO contact does not impede electron transport, opening new possibilities for the design of solar cell and optoelectronic device architectures.

In-depth insight into the structural properties of nanoparticulate NiO for CO sensing

The outstanding properties exhibited by the p-type NiO nanostructures can be greatly affected by morpho-structural and defect characteristics with constructive or competing effects. We have conducted an in-depth study on NiO nanoparticles obtained by hydrothermal synthesis and submitted to various thermal treatments, to monitor the evolution of their structural properties and the effect of the thermal history on their CO sensing. Correlated electron paramagnetic resonance and analytical transmission electron microscopy investigations evidenced an amount of up to 1 % metallic nickel clusters close to surface in the NiO nanoparticles calcined at 400 °C and 500 °C for 8 h. Subsequent annealing in vacuum and in air of the sample calcined at 400 °C resulted in different size distributions and morphology of the NiO nanoparticles and an increase/decrease of the nickel phase, respectively. Comparative CO sensing tests on the two pristine samples and on the sample calcined at 400 °C and further annealed in air at 500 °C for 2 h showed an increase in the baseline resistance of the later due to the decrease of free charge carriers induced by the dissolution of the nickel clusters. The overall CO sensing results show a strong dependence on the samples thermal history.

Silicon-based heterojunction photoanodes modified with copper-bipyridine catalyst for enhanced solar-driven water splitting

In photoelectrochemical (PEC) water splitting, accelerating the carrier transfer from the semiconductor to the catalytic functional layer through the construction of nanostructure-heterojunction interface is an effective method to overcome the intrinsically slow kinetics of the photoanode phase interface. In this work, p-type NiO and n-type TiO2 layers were deposited on the surface of n-type Si electrodes, respectively, to construct p-n and n-n heterojunction photoanodes. Moreover, a copper-bipyridine molecular catalyst, namely Cu(dcbpy), was deposited on the heterojunction photoanodes to furtherly provide transfer path for the photogenerated holes in water splitting. Under the illumination of simulated sunlight, the Si/NiO/Cu(dcbpy) photoanode exhibits a high photocurrent density of 16.63 mA cm−2 at 2.2 VRHE, which is 277.2 times of n-Si and 1.92 times of Si/TiO2/Cu(dcbpy) at the same condition. This result indicates that p-n heterojunction accelerates the photogenerated holes transfer from Si to the electrocatalyst of Cu(dcbpy) to achieve a high water-splitting efficiency. This work provides an approach to designing efficient Si-based photoanodes through nanostructure-heterojunction interface engineering and molecular catalyst modification.

A Novel GaN Superjunction FinFET Power Device With a P-Type NiO Pillar for Improved Performance

A Novel GaN Superjunction FinFET Power Device With a P-Type NiO Pillar for Improved Performance

P–N heterojunction NiO/ZnO nanowire based electrode for asymmetric supercapacitor applications

Nickel-based oxides are selected for their inexpensive cost, well-defined redox activity, and flexibility in adjusting nanostructures via optimization of the synthesis process. This communique explores the field of energy storage for hydrothermally synthesized NiO/ZnO nanowires by analysing their capacitive behaviour. The p-type NiO was successfully built onto the well-ordered mesoporous n-type ZnO matrix, resulting in the formation of p–n heterojunction artefacts with porous nanowire architectures. NiO/ZnO nanowire-based electrodes exhibited much higher electrochemical characteristics than bare NiO nanowires. The heterojunction at the interface between the NiO and ZnO nanoparticles, their specific surface area, as well as their combined synergetic influence, are accountable for the high specific capacitance (C s) of 1135 Fg−1 at a scan rate of 5 mV s−1. NiO/ZnO nanowires show an 18% dip in initial capacitance even after 6000 cycles, indicating excellent capacitance retention and low resistance validated by electrochemical impedance spectroscopy. In addition, the specific capacitance, energy and power density of the solid state asymmetric capacitor that was manufactured by employing NiO/ZnO as the positive electrode and activated carbon as the negative electrode were found to be 87 Fg−1, 23 Whkg−1 and 614 Wkg−1, respectively. The novel electrode based on NiO/ZnO demonstrates excellent electrochemical characteristics all of which point to its promising application in supercapacitor devices.

Influence of exposure time and bias voltage on the response kinetics of toluene vapour on Ho3+-doped NiO chemiresistive sensors: Yellow-emitter nanophosphors

The incorporation of rare earths (REs) into semiconducting metal oxides is advantageous for creating surface defects and manipulating electronic structures. Therefore, the hydrothermal method fabricated p-type NiO nanostructures with various holmium (Ho3+) ion concentrations of 0, 1, 2, 3, and 4 wt% are investigated. The gas sensing features of the Ho3+-doped NiO sensors were conducted at different bias voltages and exposure times. At the bias voltage of 1 V with the exposure time of 5 min, the Ho3+-doped NiO sensors displayed a relatively high response of 36.35%, detection limit and sensitivity of 449 ppb and 0.749 ppm−1, respectively towards 60 ppm toluene at 100 °C. Upon increasing the exposure time to 1 h, at the applied bias voltage of 0.5 V, the response improved by almost 6 times (Rg/Ra ∼ 201%) towards 60 ppm of toluene, showing the outstanding toluene selectivity against benzene, xylene, ethyl-benzene and acetone vapours. The gas sensing findings proved that an appropriate concentration of Ho3+ doping, exposure time and applied bias voltage have a significant influence on the sensing performances. Further tuning of these features could result in an improved sensing response. The increased sensing mechanism is assigned to the creation of oxygen vacancies.

Single-Atom Pt Doping Induced p-Type to n-Type Transition in NiO Nanosheets toward Self-Gating Modulated Electrocatalytic Hydrogen Evolution Reaction.

Exploring highly efficient single atom catalysts with defined active centers and tunable electronic structures is highly desirable. Herein, we developed an efficient hydrogen evolution reaction (HER) electrocatalyst through a self-gating phenomenon induced by Pt single atoms (SAs) supported on ultrathin NiO nanosheets (PtSA-NiO). The Ni atoms in NiO are partially replaced by the atomically dispersed Pt atoms, leading to a transition from p-type NiO into n-type PtSA-NiO. When the n-type PtSA-NiO serves as HER electrocatalyst, the self-gating phenomenon occurs in the ultrathin nanosheets, resulting in a mixture of leakage ("active") and metal-insulator-semiconductor ("inert") regions. The "inert" region induced by the ionic gating and reverse potential is capable of accumulating relatively high surface charge carrier concentration with an ultrahigh electric field, making the PtSA-NiO highly conductive; meanwhile, the HER process occurs at the Pt SAs sites (active region) in the PtSA-NiO nanosheets. As a result, the PtSA-NiO requires only 55 mV to deliver 10 mA/cm2 in an alkaline solution with good stability.