Ultraviolet Photoelectron Spectroscopy Research Articles

MXene (Ti3C2T x )/TMD (ReSe2) nanohybrid-based flexible electromechanical sensors for cervical collar strain and shoulder load detection applications

The possibly complex impacts of volunteer’s heavy backpacks, chronic neck pain are significant concerns and must be considered by the scientific and academic community. However already existing several alert systems can tackle these issues, but the evaluation approaches are costly and complicated. In this regard, ReSe2/Ti3C2T x nanohybrid based flexible sensors were fabricated by low-cost vacuum filtration technique and integrated into cervical collar strain and shoulder load detection alert systems to tackle these issues. The fabricated sensor displayed an excellent gauge factor of 14.38 and an improved sensitivity of 14.06 kPa−1. The response and recovery time of the pressure and strain sensor were 288 and 90 msec at 15% strain and 95 and 182 msec at 1.477 kPa pressure. There was a negligible degradation in performance when the pressure sensor was assessed for 5000 and the strain sensor for 4500 cycles, proving that the fabricated sensors are highly durable. The comprehensive underlying transduction mechanism is elucidated by intrinsic piezoresistive properties of nanohybrid (ReSe2/Ti3C2T x ) and Schottky barrier height mechanism with complete electronic bandstructure realization using real-time ultraviolet photoelectron spectroscopy. Also, to transfer/receive data wirelessly on an Android/ios based smartphone, the fabricated sensors were connected to an electrical circuit with a microcontroller and Bluetooth module. The effective corroboration of the ReSe2/Ti3C2T x nanohybrid based physical sensors initiates innovative prospects in the field of flexible electronics.

Fabrication of WO3[formula omitted] heterostructure photoanode by PVD for photoelectrochemical applications

The bottleneck of cost-effective green hydrogen production through the photoelectrochemical (PEC) water splitting process is lack of suitable materials. To address the material challenge, we have fabricated a heterostructure nanorod of WO3/ Fe2O3 utilizing a high-throughput radio frequency (RF) sputtering Physical vapor deposition (PVD) technique. With optimized parameters, such as as-deposited Fe of 70 nm, a deposition angle of 70°, and an annealing temperature of 500 °C, WO3/ Fe2O3 photoanodes with a morphology of vertically aligned nanorods were fabricated. A rod-like morphology with WO3 nanoparticles was synthesized by the addition of 15 nm of tungsten oxide (WO3) to the Fe2O3 nanorods. To study the optical behavior and morphology, the pristine and WO3 /Fe2O3 heterostructure thin films were characterized by ultraviolet photoelectron spectroscopy (UPS), ultraviolet UV, X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). This has led to a 5-fold improvement in PEC performance (0.588 mA/cm2 at 1.23 V vs. RHE for the mixture compared to 0.122 mA/cm2 at 1.23 V vs. RHE for the pristine). As a co-catalyst, WO3 successfully suppressed recombination and assisted in the hole transfer, which immediately increased the photocurrent density of fabricated photoanodes. This was illustrated via the electrochemical impedance spectra including both Nyquist and Mott-Schottky plots with or without illumination. When sustained in steady illumination for 900 s, this photoanode displayed highly stable behavior under PEC conditions.

Adsorption and surface reactions of C2H2 and C2H4 on Co(0001)

In this paper we have studied adsorption and surface reactions of acetylene and ethylene on Co(0001) in detail by temperature desorption spectrum (TDS), X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS). C2H4 adsorption at 130 and 300 K followed by subsequent heating mainly forms C2 clusters and graphitic carbon, respectively, while C2H4 decomposes at 400 and 500 K to form dominant graphitic carbon and carbon adatoms, respectively. C2H2 molecularly adsorbs at 130 K but exclusively dehydrogenates upon heating. The resulting C2H2(a) species at low coverages remains stable up to 400 K and then exclusively dehydrogenates into C2 clusters, while the resulting C2H2(a) species at high coverages remains stable up to 310 K and then majorly dehydrocyclizates into (C2H)n intermediates with ring structures at 340 K which further dehydrogenates into graphitic carbon, and minorly dehydrogenates into C2 clusters. Exposed at 370 K, C2H2 dehydrocyclizates into (C2H)n intermediates with ring structures. These temperature and coverage dependent surface reactions of C2H2 and C2H4 on Co(0001) greatly enrich our fundamental understanding of Co-catalyzed F-T synthesis reaction.

Built-in Electric Field-Induced Work Function Reduction in C-Co3O4 for Efficient Electrochemical Nitrogen Reduction.

Co3O4 is a highly selective catalyst for the electrochemical conversion of N2 to NH3. However, the large work function (WF) of Co3O4 leads to unsatisfactory activity. To address this issue, a strong built-in electric field (BIEF) was constructed in Co3O4 by doping C atoms (C-Co3O4) to reduce the WF for improving the electrocatalytic performance. C-Co3O4 exhibited a remarkable NH3 yield of 38.5 μg h-1 mgcat-1 and a promoted FE of 15.1% at -0.3 V vs RHE, which were 2.2 and 1.9 times higher than those of pure Co3O4, respectively. Kelvin probe force microscopy (KPFM), zeta potential, and ultraviolet photoelectron spectrometry (UPS) confirmed the formation of strong BIEF and WF reduction in C-Co3O4. Additionally, in situ Raman measurements and density functional theory (DFT) calculations revealed the relationship between BIEF and WF and provided insights into the reaction mechanism. Our work offers valuable guidance for the design and development of more efficient nitrogen reduction catalysts.

Effect of energy band alignments in carbon doped ZnO/TiO2 hybrid heterojunction photocatalyst on the photodegradation of ofloxacin

The present study highlights the influence and efficacy of a self-doped carbon (C)–ZnO/TiO2 hybrid heterojunction for the photocatalytic degradation of ofloxacin (OFX) in aqueous media. The flower-like hybrid heterojunction was prepared via hydrothermal treatment at varying concentrations of ZnO and TiO2. C doping was internally introduced to the ZnO lattice by the decomposition of polyvinylpyrrolidone as a source to achieve better band alignment. A systematic investigation was performed to elucidate the mechanism of photodegradation by the heterojunction via analyzing the parameters such as composition, dosage, and pH of the system. The optimized sample 1:2 (Zn: Ti) ratio exhibited a photodegradation efficiency of 99.9% for OFX within 60 min, demonstrating a reaction rate 1.6 times higher than that of C–ZnO. Moreover, the involvement of charge carriers was analyzed through scavenging experiments. The results showed that trapping superoxide anions resulted in a 57.8% reduction in photoactivity, confirming their significant involvement in the process. The n-doping of C and subsequent defects level formation in the heterojunction hybrid was supported by X-ray photoelectron spectroscopy. The mechanism for the effective and extended photodegradation of hybrid heterojunctions was proposed by investigating band-gap using Tauc plot and valence band spectra using ultraviolet photoelectron spectroscopy. The valence band spectra verified the uplift of energy bands via doping, confirming the strong reducing power of the heterojunction hybrids. Additionally, liquid chromatography-mass spectroscopy was employed to perform the identification of the degradation pathway and intermediates.

Control of intrinsic polarity for work function modulation of polyvinylidene fluoride crystalline phases

Ferroelectric polymers with high flexibility and inherent piezo- and pyro-electric properties have gained tremendous importance for next-generation wearable electronics. In this context, we investigate the intrinsic polarity mediated work function modulation in α-, γ-, and β-crystalline phases of a ferroelectric polymer, namely, polyvinylidene fluoride. A wide range of surface potentials (i.e., −5 to −70 V) were observed depending upon the crystalline polymorph and their surface morphologies. For example, upon nucleation of electroactive γ- and β-phases, a reduction in spherulite size is observed in comparison to its α-counterpart. Ultraviolet photoelectron spectroscopy was employed to realize the effect of surface potential on the valence bands spectrum. In particular, the work function of the non-electroactive α-phase (φα ∼ 5.09 eV) significantly increased when it is converted into the electroactive γ (φγ ∼ 5.99 eV) and β (φβ ∼ 7.39 eV) phases. The advantage of surface potential variation is shown by synergistic charge generation as a result of contact electrification of single active material-based polar interfaces with different work functions.

Rational Fabrication of Fe3O4/Co3O4/Graphdiyne Tandem Heterojunction toward Optimized Photocatalytic Hydrogen Evolution

Graphdiyne (GDY) is a novel two‐dimensional material composed of sp and sp2 hybridized carbon atoms. Herein, GDY nanosheets are prepared from tribromobenzene by a simple ball‐milling‐assisted reduction–elimination method and is introduced into Fe3O4 colloidal spheres and Co3O4 cubes by low‐temperature mixing to efficiently synthesize Fe3O4/Co3O4/GDY tandem heterojunction photocatalysts. The hydrogen evolution activity of the optimized catalyst is 4.02 mmol g−1 h−1 under visible light (λ ≥ 420 nm), which is 100.05, 10.05, and 3.65 times higher than that of Fe3O4 (0.04 mmol g−1 h−1), Co3O4 (0.40 mmol g−1 h−1), and GDY (1.10 mmol g−1 h−1), respectively. In addition, the Prussian blue analog (PBA)‐derived Co3O4 improves the light‐harvesting efficiency and reaction kinetics. More importantly, the establishment of tandem heterojunctions prompts energy‐level alignment and optimizes charge multichannel transfer, which is the dominant factor for enhanced photocatalytic activity. Combined with time‐resolved photoluminescence spectra, valence band X‐Ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, and density functional theory calculations, the possible mechanism of Fe3O4/Co3O4/GDY series heterojunction is proposed and elucidated. This work provides a new idea for the construction of tandem heterojunctions based on graphdiyne and PBA derivatives.

Dual-plasma enhanced 2D/2D/2D g-C3N4/Pd/MoO3-x S-scheme heterojunction for high-selectivity photocatalytic CO2 reduction

The localized surface plasmon resonance (LSPR) effect has shown significant progress in enhancing the efficiency of light absorption and separating photogenerated carriers. Herein, the dual-plasma enhanced 2D/2D/2D g-C3N4/Pd/MoO3-x (CPM) S-scheme heterojunction photocatalysts were synthesized using the method of hydrothermal and electrostatic self-assembly for high-selectivity photocatalytic reduction of CO2 to produce CO. The dual LSPR effect of MoO3-x and ultrathin Pd nanosheets synergistically broadened the optical response range of the CPM composites and successfully improved the photocatalytic activity and near-infrared (NIR) performance. The optimized CPM-30 photocatalysts exhibited CO yields of 18.55 μmol g−1 with a selectivity of 96.3%. In addition, the CO yield reached 3.92 μmol g−1 after 4 h of NIR light photoirradiation. The electron spin resonance (ESR) and ultraviolet photoelectron spectroscopy (UPS) tests showed that the S-scheme heterojunctions were constructed by coupling g-C3N4/Pd nanosheets and MoO3-x. This work will provide a reference for improving product selectivity through the design of two-dimensional composites and the utilization of plasma materials.

Construction of Co9S8/MoS2/Ni2P double S-scheme heterojunction for enhanced photocatalytic hydrogen evolution

Rational design of composite catalysts with efficient charge separation and transfer and good light collection ability is of great significance to achieve high photoelectrochemical conversion efficiency. In this paper, a Co9S8/MoS2/Ni2P dual S-scheme heterojunction photocatalyst was successfully synthesized by a simple sulfidation and hydrothermal method. The optimized Co9S8/MoS2/Ni2P composite with hierarchical structure, large surface area and numerous reactive active sites showed a good photocatalytic hydrogen evolution rate of 5.69 mmol g−1 h−1, which is 2.28, 4.12 and 10.74 times higher than that of pure Co9S8, MoS2 and Ni2P, respectively. A combination of time-resolved photoluminescence (TRPL) spectroscopy, valence band XPS (VB-XPS), ultraviolet photoelectron spectroscopy (UPS), and density-functional theory (DFT) calculations confirms that the formation of the Co9S8/MoS2/Ni2P double S-scheme greatly facilitates charge migration and spatial separation, and improves the oxidation and reduction ability. This work will provide insights into the development of PBA-based dual S-scheme heterojunction catalysts for photocatalytic hydrogen evolution.

Evidence of charge transfer across the organic-inorganic hetero-junction based visible light driven photo-catalyst

Organic-inorganic hetero-junction based catalysts with efficient charge separation ability for superior photo-catalytic activity have been developed by chemical methods. Titanium dioxide (TiO2) and polypyrrole (PPy) as single photo-catalyst have been investigated and compared with TiO2/PPy hetero-junction composite. TiO2/PPy composite has enhanced efficiency for the degradation of toxic organic dye methylene blue (MB) through the charge transfer route. Broad curves in UV-Vis spectra arise due to polaron and bipolaron in PPy and TiO2/PPy composite. The de-localized polaron (Landé g factor value of 1.99) was further detected by electron spin resonance (ESR). The effect of polaron-bipolaron on the structure of as-synthesized PPy and TiO2/PPy composite has been explored by Raman spectroscopy. The oxidation state of different species and electronic structures below the Fermi level has been investigated by x-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS), which provides molecular orbitals insight and charge transfer state across the hetero-junction TiO2/PPy composite. Collectively, UPS and UV-Vis spectroscopy gives the energy positions (valence/ HOMO band and conduction band (C.B.)/LUMO) for TiO2 and PPy having straggled type band alignment which confirms the hetero junction in the composite.

Improving the Stability of Li Metal Anode/Solid Electrolyte Interfaces via an Li3PO4 Intermediate Layer: An Investigation of Surface Chemistry and Electronic Band Structure

Recently, researchers are extensively developing next-generation batteries, including all-solid-state batteries (ASSBs), to meet the increasing demand for electric vehicles (EVs) and renewable energy storage. Li metal has been considered an ideal anode material due to its high theoretical capacity and low redox potential. However, it is highly reactive and severe side reactions occur at the interface between Li metal anode and solid electrolytes (SEs), significantly affecting battery performance. Therefore, Li metal anodes have not yet been commercialized. To obtain a chemically stable Li metal anode, the authors examined the side reactions at the interface between the Li metal anode and oxide-type SE using surface analysis techniques such as time-of-flight secondary ion mass spectrometry (TOF-SIMS), X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS) and low-energy inverse photoelectron spectroscopy (LEIPS). In this paper, we present the results of interface analysis between Li metal anode/SE and discuss how to obtain a stable Li metal anode.

Solution processable visible-light and color-selective image sensor with a ZnO/QDs/ZrO2 sandwich structure

Quantum dots (QDs) are emerging materials for optoelectronic devices because of their facile tunable bandgap and solution processability. However, overcoming inherent problems, such as vulnerability to atmospheric moisture and the persistence photoconductivity (PPC) effect originating from trap states, is necessary. We proposed a method to enhance the stability and reduce the PPC effect by adding a ZrO2 passivation layer above the QDs layer. The ZrO2 layer effectively reduced the trap state of the QDs, passivated the QDs from external environmental oxygen and moisture, and simultaneously acted as an additional channel. Interfacial analyses were conducted using X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), time-resolved photoluminescence (TRPL), and high-resolution transmission electron microscopy (HR-TEM) measurements. Hence, the device showed enhanced photoresponsivity and photosensitivity of 2.6 × 103 A/W and 6.67 × 105, respectively. Additionally, the device showed a highly reduced PPC effect with a rate of current increase of 0.017 under periodic 635 nm wavelength light illumination. Moreover, it showed reliable long-term stability over 30 days under a relative humidity of ∼40%. Therefore, a color-selective image sensor was successfully demonstrated, and the device could recognize red/green/blue colors owing to its reduced PPC effect and high stability. Our results suggest a useful method for developing next-generation QD-based transparent optoelectronic devices.

Enhancing perovskite solar cells efficiency through cesium fluoride mediated surface lead iodide modulation

The presence of an excessive amount of lead iodide on the surface of perovskite solar cells (PSCs) is a significant contributing factor that adversely affects the stability of these devices when exposed to continuous light. To address this issue, we developed an effective strategy involving polishing PbI2 on a perovskite surface using CsF. In this study, we investigated the effects of CsF post-treatment on perovskite films and their photovoltaic properties. The results of the time-resolved photoluminescence and ultraviolet photoelectron spectroscopy tests reveal the significant positive impact of our passivation method based on CsF, which reduces the valence band offset between the perovskite and hole transport layers while simultaneously enhancing the carrier interface transport. PSCs treated with CsF exhibited a photoelectric conversion efficiency (PCE) of 24.25% and an increased fill factor (FF) of 81.72%, which surpassed those of the original PSCs (PCE = 22.12% and FF = 77.40%). Furthermore, after aging for over 2500 h at room temperature and in 30 ± 10% humidity, the PCE of the unpacked PSCs reduced to only 42% of the initial value. Furthermore, the devices treated with CsF maintained their impressive performance, with the PCE maintaining optimal levels at 91% of the initial efficiency.

WO3 work function enhancement induced by filamentous films deposited by resistive heating evaporation technique

Tungsten trioxide (WO3) films are of great interest due to their electronic properties which can be tuned by surface nanostructuring leading to enhanced efficiency for gas sensing, energy storage or electrochromic applications. Resistive heating of tungsten (W) filaments at pressures of few Pa in an oxygen O2 atmosphere has already demonstrated its capability to form porous, micro/nano-structured, cheap and fast films making it suitable for industrial applications. This work presents stoichiometric WO3 films produced by applying a current into a W filament for pressures in the range of 2–20 Pa. The increase of the pressure above 7.5 Pa led to amorphous WO3 films with a newly filamentous morphology. As a function of the pressure, the work function (WF) of the films was determined in-vacuo by aims of Ultraviolet Photoelectron Spectroscopy (UPS). In addition to the high surface to volume ratio of the films, the WF exhibited an increase from 5.8 eV, for a conventional WO3 film, to a maximum of 8.7 eV at 20 Pa. This change corresponds to an increase of the WF of about 50% compared to 5.8 eV making our films suitable for a large variety of applications. The highering of the WF is mainly induced by the change of morphology to filamentous structures, the defect induced by the amorphous structure and the nanometric size of the filaments leading to the confinement of the electrons in the valence band for our WO3 films. Additionally, a change from p to n-type polarity is reported in-vacuo when increasing the pressure from 7.5 to 20 Pa with the formation of an intermediate band at around 0.8 eV below the Fermi level. Additionally, molybdenum trioxide (MoO3) and vanadium pentoxide (V2O5) filamentous films were deposited via the resistive evaporation technique in an O2 atmosphere. Similarly, copper, aluminium and molybdenum wires were used, leading to the formation of islands having foam-like structures analogous to the WO3.

Interfacial engineering of hematite photoanodes toward high water splitting performance

Efficient and scalable photoelectrochemical water splitting electrode designs are a challenge. This study focuses on hafnium-modified hematite (X%Hf-HEM) photoanodes, prepared via spin-coating polymeric precursor solutions with varying Hf4+/Fe3+ (mol) ratios (1.0%, 3.0%, 4.0%, and 5.0%) onto fluorine-doped tin oxide substrates. Structural, morphological, and compositional analyses confirm pure hematite phases in all X%Hf-HEM samples. Increasing Hf4+ content correlated with reduced grain size, thickness, and surface roughness due to Hf4+ segregation at grain boundaries during thermal treatment. Hafnium segregation at hematite grain boundaries and hematite|fluorine-doped tin oxide interfaces is confirmed using scanning transmission electron microscopy coupled with energy dispersive spectroscopy. Notably, the 4%Hf-HEM photoanode exhibits exceptional efficiency enhancement, outperforming HEM efficiency by 4.5 times. Gas chromatography results highlight O2 and H2 evolution rates of 14.49 ± 0.09 μmol/cm2/h and 8.1 ± 0.5 μmol/cm2/h, respectively, for 4%Hf-HEM, with a H2/O2 ratio close to 2:1. The charge dynamics investigated from intensity-modulated photocurrent spectroscopy evidence the main Hf4+ effect of improving charge separation, achieving greater efficiency for 4%Hf-HEM. Shifts in valence band maximum from ultraviolet photoelectron spectroscopy measurements indicate surface state presence, supported by ηtransfer trends calculated from intensity-modulated photocurrent spectroscopy. This research presents a scalable, cost-effective approach to multiinterface photoanode development, holding promise for innovative photoelectrochemical water splitting technologies.

Work function measurement by ultraviolet photoelectron spectroscopy: Versailles project on advanced materials and standards interlaboratory study

We present the results of an interlaboratory study on work function (WF) measurements by ultraviolet photoelectron spectroscopy (UPS) conducted under the auspices of the Versailles Project on Advanced Materials and Standards. Two samples, gold (Au) film deposited on a flat Si(100) and highly oriented pyrolytic graphite (HOPG), were distributed to six different laboratories. Prior to UPS measurements, the samples underwent common sample pre-cleaning procedures: wet treatment and Ar+-sputtering in a vacuum for Au, and mechanical peeling in air for HOPG. Instrumental settings are adjusted for energy-scale calibration and sample bias optimization. The average reference WF value (WFref) and its expanded uncertainty (Uref) were calculated from each dataset that participants provided. The results of the Au sample demonstrated 5.40 ± 0.13 eV after Ar+ sputtering in vacuum, while the HOPG sample showed 4.62 ± 0.16 eV after mechanical peeling-off. Even though the participants used slightly different sample bias voltages and sample cleaning methods with various instruments, the results demonstrate remarkable consistency. Their consistency among the laboratories for both samples with high and low WF values provides a basis for establishing a new international standard for UPS in the surface chemical analysis community.

Insights into the Semiconductor SERS Activity: The Impact of the Defect-Induced Energy Band Offset and Electron Lifetime Change.

The significant boost in surface-enhanced Raman scattering (SERS) by the chemical enhancement of semiconducting oxides is a pivotal finding. It offers a prospective path toward high uniformity and low-cost SERS substrates. However, a detailed understanding of factors that influence the charge transfer process is still insufficient. Herein, we reveal the important role of defect-induced band offset and electron lifetime change in SERS evolution observed in a MoO3 oxide semiconductor. By modulating the density of oxygen vacancy defects using ultraviolet (UV) light irradiation, SERS is found to be improved with irradiation time in the first place, but such improvement later deteriorates for prolonged irradiation even if more defects are generated. Insights into the observed SERS evolution are provided by ultraviolet photoelectron spectroscopy and femtosecond time-resolved transient absorption spectroscopy measurements. Results reveal that (1) a suitable offset between the energy band of the substrate and the orbitals of molecules is facilitated by a certain defect density and (2) defect states with relatively long electron lifetime are essential to achieve optimal SERS performance.

Investigation of the effect of different types of SiN layers and cap-GaN on the surface electronic states of AlGaN/GaN heterostructures with 2DEG using X-ray and UV photoelectron spectroscopy

Determining the effect of different crystalline and amorphous passivation layers on the electronic states and surface properties of III-nitride heterostructures is an important task from the point of view of improving the performance of modern microwave and power electronic devices. In the present work the effect of in situ deposited gallium nitride and silicon nitride passivation layers on the surface electronic states of AlGaN/GaN heterostructures with a two-dimensional electron gas is investigated using the X-ray, ultraviolet and angle-resolved ultraviolet photoelectron spectroscopy (XPS, UPS, ARUPS) techniques. A thorough analysis of the experimental UPS spectra was carried out, the primary photoelectrons were extracted from the experimental spectra and the contribution of the electron states on the surface in the energy range of the AlGaN bandgap was identified. It was found that the density of states on the surface decreases by about an order of magnitude in the AlGaN bandgap during the formation of a silicon nitride layer. For the first time, it was found that a significant decrease in the density of surface states (up to a factor of 6) is observed even at extremely low thickness of the SiN ordered layer formation with the (√3 × √3)R30° superstructure.

Non-contact approach to extract Schottky barrier characteristics for gas sensitive nanostructured interfaces

Formation of high precision nanorod based surface morphologies can be engineered with nanotechnology to mimic the function of sensory hairs. Gas sensitive I-V characteristics unique to these surfaces require initialisation under voltage bias and temperature elevation to exploit their band structures and therefore achieve optimal gas response. Prior to detection, devising effective approaches to optimise nanorod based sensors can provide access and efficient control to downsize and significantly miniaturise current gas sensors. In this work, we devised a novel non-contact analysis approach via ultraviolet photoelectron spectroscopy (UPS) to extract specific band structure parameters specifically to locate particular bias for optimal sensor initialisation. The results from five cases all indicate how fabricated nanostructured Schottky barrier heights can be evaluated from UPS data and how their I-V data are correlated and also validate our band structure postulations. The obtained Schottky barrier height values from simulated band structures provided an optimal biasing condition of 0.8 V for Au-ZnO nanorod hydrogen gas sensory operation at 150 °C, demonstrating experimental validity with gas-electrical measurements. Further, the gas response data show exponential dependence with gas concentration which is highly relevant for programmable trigger response controlled sensing function based applications.

Highly Efficient All-Solution-Processed Quantum Dot Light-Emitting Diodes Using MoOx Nanoparticle Hole Injection Layer.

This paper presents a study that aims to enhance the performance of quantum dot light-emitting didoes (QLEDs) by employing a solution-processed molybdenum oxide (MoOx) nanoparticle (NP) as a hole injection layer (HIL). The study investigates the impact of varying the concentrations of the MoOx NP layer on device characteristics and delves into the underlying mechanisms that contribute to the observed enhancements. Experimental techniques such as an X-ray diffraction and field-emission transmission electron microscopy were employed to confirm the formation of MoOx NPs during the synthesis process. Ultraviolet photoelectron spectroscopy was employed to analyze the electron structure of the QLEDs. Remarkable enhancements in device performance were achieved for the QLED by employing an 8 mg/mL concentration of MoOx nanoparticles. This configuration attains a maximum luminance of 69,240.7 cd/cm2, a maximum current efficiency of 56.0 cd/A, and a maximum external quantum efficiency (EQE) of 13.2%. The obtained results signify notable progress in comparison to those for QLED without HIL, and studies that utilize the widely used poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) HIL. They exhibit a remarkable enhancements of 59.5% and 26.4% in maximum current efficiency, respectively, as well as significant improvements of 42.7% and 20.0% in maximum EQE, respectively. This study opens up new possibilities for the selection of HIL and the fabrication of solution-processed QLEDs, contributing to the potential commercialization of these devices in the future.