Electrical Optical Properties Research Articles

Polymer blend compositions reliant comprehensive study on optical, thermal, structural, and broadband dielectric and electrical properties of P(VDF-HFP)/PMMA films

Polymer blend compositions reliant comprehensive study on optical, thermal, structural, and broadband dielectric and electrical properties of P(VDF-HFP)/PMMA films

Thermochromic properties and surface chemical states of reactive magnetron sputtered vanadium oxide thin films at various deposition pressures

Vanadium oxide thin films were prepared using reactive magnetron sputtering method, varying the deposition pressures from 4 to 10 mTorr while maintaining the other sputtering parameters constant. Our investigations revealed sensitive dependence of deposition pressure, chemical states of the V and O atoms, crystal phases, and thermochromic (TC) optical modulation. Specifically, the film deposited at 8 mTorr displayed distinct TC characteristics with a prevalent monoclinic m-VO2 phase according to X-ray diffraction (XRD), supported by X-ray photoelectron spectroscopy (XPS). Optical transmittance modulation and electrical property measurements revealed a metal–insulator transition (MIT), confirming the intimate connection between TC characteristics and presence of the m-VO2 phase. Films deposited at pressures lower or higher than 8 mTorr exhibited typical semiconductor behavior without TC characteristics, further supported by in situ XRD, where (110) plane shifted to lower angle upon heating above τC. Chemical state analysis by XPS revealed a clear correlation between V−O peaks and the presence of a VO2 phase, with the film deposited at 8 mTorr displaying relatively large peak fitted area indicative of the VO2 phase. These findings highlight the critical and sensitive dependence of the deposition conditions in tailoring the properties of vanadium oxide thin films and provide valuable insights for potential applications in chromogenic films.

Rational Strategies to Improve the Efficiency of 2D Perovskite Solar Cells.

In the quest for durable photovoltaic devices, 2D halide perovskites have emerged as a focus of extensive research. However, the reduced dimension in structure is accompanied by inferior optical-electrical properties, such as widened band gap, enhanced exciton binding energy, and obstructed charge transport. As a result, the efficiency of 2D perovskite solar cells (PSCs) lags significantly behind their 3D counterparts. To overcome these constraints, extensive investigations into materials and processing techniques are pursued rigorously to augment the efficiency of 2D PSCs. Herein, The cutting-edge delve into developments in 2D PSCs, with a focus on chemical and material engineering, as well as their structure and photovoltaic properties. The review starts with an introduction of the crystal structure, followed by the key evaluation criteria of 2D PSCs. Then, the strategies around solution chemical engineering, processing technique, and interface optimization, to simultaneously boost efficiency and stability are systematically discussed. Finally, the challenges and perspectives associated with 2D perovskites to provide insights into potential improvements in photovoltaic performance will be outlined.

Computational modeling of CH4 and CO2 adsorption on monolayer graphenylene: Implications for optoelectronic properties and hydrogen production

Graphenylene (GP) is a two–dimensional carbon allotrope with a hexagonal lattice structure containing periodic pores. The unique arrangement of GP offers potential applications in electronics, optoelectronics, energy storage, and gas separation. Specifically, its advantageous electronic and optical properties, make it a promising candidate for hydrogen production and advanced electronic devices. In this study, we employ a computational chemistry–based modeling approach to investigate the adsorption mechanisms of CH4 and CO2 on monolayer GP, with a specific focus on their effects on optical adsorption and electrical transport properties at room temperature. To simulate the adsorption dynamics as closely as possible to experimental conditions, we utilize the self–consistent charge tight–binding density functional theory (SCC–DFTB). Through semi–classical molecular dynamics (MD) simulations, we observe the formation of H2 molecules from the dissociation of CH4 and the formation of CO + O species from carbon dioxide molecules. This provides insights into the adsorption and dispersion mechanisms of CH4 and CO2 on GP. Furthermore, we explore the impact of molecular adsorption on optical absorption properties. Our results demonstrate that CH4 and CH2 affects drastically the optical adsorption of GP, while CO2 does not significantly affect the optical properties of the two–dimensional material. To analyze electron transport, we employ the open–boundary non–equilibrium Green's function method. By studying the conductivity of GP and graphene under voltage bias up to 300 mV, we gain valuable insights into the electrical transport properties of GP under optical absorption conditions. The findings from our computational modeling approach might contribute to a deeper understanding of the potential applications of GP in hydrogen production and advanced electronic devices.

EFFECT OF DIFFERENT UV EXPOSURE ENERGY ON POLYIMIDE-BASED NONVOLATILE RESISTIVE PHOTOMEMORY DEVICE

Recently, many researchers pay attractive attention to organic memory technology. Polyimide film was used as the resistive switching layer of nonvolatile photomemory in this study. In order to improve the performance of the device, different wavelengths of Ultraviolet (UV) light were used to operate the device, and its impact on the polyimide film was discussed. In this paper, three different UV light bands, UVA, UVB, and UVC, are used to switch devices between low resistance state (LRS) and high resistance state (HRS). It can be seen from the results that all three kinds of energies of UV light can transform the polyimide film from HRS to LRS successfully. According to the data, after 1s of UVB irradiation, the LRS current of polyimide-based photomemory device is the largest, and the data retention ability is also the best, the second is to irradiate UVA, and the last is to irradiate UVC. The results of the optical properties and electrical properties are coincidental. Therefore, different UV energies can affect this photomemory device.

Bandgap-graded Cu2Sn1-xGexS3 thin film solar cells prepared by sputtering SnGe/Cu targets

Cu2Sn1-xGexS3 (CTGS) thin films were created through sulfurizing SnGe/Cu precursors deposited by the sputtering method. The effects of different sulfurization conditions on the crystallinity, morphology, composition, optical-electrical properties and chemical information of the CTGS thin films have been investigated in detail. The results demonstrate that the CTGS thin films obtained by using sulfurization temperature at 550 °C for 20min have the best crystal quality and smooth surface morphology with largest grains and the best optical-electrical properties. Meanwhile, CTGS thin films solar cell with the best performance is found that the CTGS film possesses a graded band gap structure, in which the band gap gradually become larger towards the Mo electrode, and the CdS/CTGS hetero-junction interface shows the “type I″ energy band alignment with a “spike-like” structure. As a result, the obtained bandgap-graded CTGS thin film solar cells with the best power conversion efficiency (PCE) of 3.35 (±0.04) % manifest an open-circuit voltage of 389 (±7.78) mV and a short-circuit current density of 26.98 (±0.54) mA cm−2. This work demonstrates a promising route to develop high-efficiency Cu(In,Ga)Se2 or Cu2SnS3-based thin film solar cells.

Ionic Liquids Microenvironment Modulates the Interface Properties of g-C3N4 for Boosting the Performance of Photodegradation and Infected Wound-Healing Therapy.

The improvement of photocatalytic activity of g-C3N4 is expected for its advanced applications but remains a challenge due to the limitations of current strategies, such as single function, inefficiency, and uneconomical. Herein, a modified g-C3N4 with improved interface properties is constructed through the modulation of the ionic microenvironment affected by ionic liquids (ILs) and exhibits a 2.3-fold enhanced photodegradation efficiency and a 3.5-fold enhanced reaction rate relative to pristine g-C3N4. It has demonstrated excellent performance in photo-therapy bacterial-infected wounds. Theoretical calculation indicated that the precursor can be regulated by designing the specific ILs microenvironment to form "ILs-Mel" clusters due to the diversity of interaction energy and electrostatic potential. The cluster results in uneven stress on the 2D plane, further inducing the reconstruction of the microstructure. The synergistic effect of cations and anions of ILs on regulating the interface properties of g-C3N4 due to the change of skeleton structure during thermolysis of ILs. The microstructure, surface, and optical-electrical properties can be adjusted by selecting different cations of ILs, and the custom-made band structure and wettability can be obtained by selecting different anions. This work provides a facile strategy to modulate the interface properties of g-C3N4 by building specific a microenvironment of precursor.

Reliability of transparent conductive oxide in ambient acid and implications for silicon solar cells

Transparent conductive oxide (TCO) films, known for their role as carrier transport layers in solar cells, can be adversely affected by hydrolysis products from encapsulants. In this study, we explored the morphology, optical-electrical properties, and deterioration mechanisms of In2O3-based TCO films under acetic acid stress. A reduction in film thickness and carrier concentration due to acid-induced corrosion was observed. X-ray photoelectron spectroscopy and inductively coupled plasma emission spectrometry analyses revealed that TCOs doped with less-reactive metals exhibited enhanced corrosion resistance. The efficiency of silicon heterojunction (SHJ) solar cells with tin-doped indium oxide, titanium-doped indium oxide, and zinc-doped indium oxide films decreased by 10%, 26%, and 100%, respectively, after 200 ​h of corrosion. We also found that tungsten-doped indium oxide could effectively safeguard SHJ solar cells against acetic acid corrosion, which offers a potential option for achieving long-term stability and lower levelized cost of solar cell systems. This research provides essential insights into selecting TCO films for solar cells and highlights the implications of ethylene-vinyl acetate hydrolysis for photovoltaic modules.

Investigation of optical transitions and electrical properties in LaVO3/SrTiO3 heterostructure

Investigation of optical transitions and electrical properties in LaVO3/SrTiO3 heterostructure

Optimization of Semiconductor-Based SRR Metamaterials as Sensors

The development of hybrid sensor media is needed to achieve more efficient, sensitive, and accurate performance. Efforts to modify the structure of conventional metamaterials are carried out by integrating semiconductor materials which aim to improve the characteristics of optical properties, electrical properties, and sensitivity as sensors. This study aims to analyze and investigate changes in the optical properties of semiconductor-based metamaterials. The research was conducted through simulation and numerical methods to design and characterize the SRR metamaterial geometry, with a modified Nicolson-Ross-Weir approach, especially the optical parameters of refractive index. The single-cell square pattern SRR metamaterial geometry with a ring radius of 2.2 – 2.8 mm on quartz glass substrate designed at a smaller wavelength based on a maximum frequency source of 9 GHz. The square SRR metamaterial is integrated with several semiconductor materials such as silicon (Si), gallium arsenide (GaAs), and aluminum nitride (AlN). Changes in radius size cause a redshift with respect to radius enlargement. The increasing ring radius of SRR causes a higher resonance depth of the refractive index. Combining hybrid semiconductors with metamaterial results in more negative metamaterial properties as the refractive index becomes larger and negative. The addition of semiconductor material to the metamaterial substrate causes a negative refractive index to shift to a lower frequency.

Investigation of structural, optical, and electrical properties of PEDOT:PSS/Au/PEDOT:PSS multilayer films

PEDOT:PSS/Au/PEDOT:PSS multilayer films were successfully prepared and investigated. The PEDOT:PSS and Au layers were prepared using spin coating and DC sputtering, respectively. The thickness of the Au layer was varied within the range of 2–10 nm to investigate its impact on the resulting multilayer films. The amorphous nature of the multilayer films was interpreted from X-ray diffraction analysis. Fourier-transform infrared spectroscopy identified that the multilayer films were the major surface chemical structure of PEDOT:PSS. The optical transmittance and sheet resistance characteristics of the multilayer films exhibited a significant reduction owing to the presence of the Au interlayer. In order to evaluate the optical-electrical properties of the multilayer films, a figure of merit (FOM) was calculated. Remarkably, the multilayer films featuring a thin Au layer of 2 nm yielded the highest FOM value. Therefore, it can be demonstrated that multilayer films of PEDOT:PSS/Au/PEDOT:PSS fabricated with a thin Au layer can be applicable for utilization in optoelectronic devices.

Tuning the Inter-Nanoplatelet Distance and Coupling Strength by Thermally Induced Ligand Decomposition.

CdSe nanoplatelets (NPLs) are promising 2D semiconductors for optoelectronic applications, in which efficient charge transport properties are desirable. It is reported that thermal annealing constitutes an effective strategy to control the optical absorption and electrical properties of CdSe NPLs by tuning the inter-NPL distance. Combining optical absorption, transmission electron microscopy, and thermogravimetric analysis, it is revealed that the thermal decomposition of ligands (e.g., cadmium myristate) governs the inter-NPL distance and thus the inter-NPL electronic coupling strength. Employing ultrafast terahertz spectroscopy, it is shown that this enhanced electronic coupling increases both the free carrier generation efficiency and the short-range mobility in NPL solids. The results show a straightforward method of controlling the interfacial electronic coupling strength for developing functional optoelectronic devices through thermal treatments.

Electrostatic discharge induced degradation of optical-electrical properties and defect evolution of GaAs-based oxide-confined VCSELs.

GaAs-based oxide-confined vertical-cavity surface-emitting lasers (VCSELs) exhibit relatively low resistance against reliability-related damage. In order to gain a deeper understanding of the degradation and failure mechanism in oxide-confined VCSELs caused by electrostatic discharge (ESD)-induced defect proliferation, we investigated the effects of ESD stress on the degradation of optical-electrical characteristics and the evolution of defects in VCSELs under human body model test condition. The degradation threshold values for forward and reverse ESD pulse amplitudes were estimated to be 200 V and -50 V, respectively. Notably, VCSELs demonstrated greater sensitivity to reverse bias ESD compared to forward bias ESD. Analysis of optical emission and microstructure provided evidence that the device failure is attributed to an increase in ESD current density, leading to the multiplication of dark line defects (DLDs) originating from the edge of the device's oxide aperture. The formation of defects occurred suddenly in discrete events within small regions, rather than progressing gradually and uniformly. These defects propagated and led to damage across the entire active region. We believe that our results would be meaningful for improving the reliability of VCSEL in the future.

Modulation of optical absorption and electrical properties in Mn-Co-Ni-O-based high-entropy thin films

High-entropy thin films of Mn0.6Co0.6Ni0.6Mg0.6Cu0.6O4, Mn0.6Co0.6Ni0.6Mg0.6 Zn0.6O4, and Mn0.6Co0.6Ni0.6Cu0.6Zn0.6O4 (MCNMC, MCNMZ, and MCNCZ) with equiatomic proportions were synthesized using chemical solution deposition on silicon substrates. Structural analysis confirmed a consistent face-centered cubic spinel structure, while significant differences in surface morphology were observed. Quantification of the valence states of Mn ions revealed an inverse variation in the concentrations of Mn4+ and Mn2+ ions. The heightened infrared light absorption of the MCNMC thin film was assigned to Cu-induced Jahn-Teller distortion and highly polarized Mg-O bonds. All samples exhibited negative temperature coefficient behaviors in their electrical properties. Additionally, the MCNMC thin film demonstrated the lowest resistance due to its denser microstructure, close proximity of Mn3+/Mn4+ ion concentrations, and additional Cu+/Cu2+ ion pairs, enhancing small polaron hopping conductivity. In contrast, the MCNMZ thin film showed moderate resistance but boasted the highest thermal constant (B25/50) of 3768 K, attributed to its distinctive grain chain structure, facilitating carrier transport while introducing migration barriers.

Temperature sensitivity of adjustable band gaps of Sb2(S, Se)3 solar cells via vapor transport deposition

Quasi-one-dimensional antimony chalcogenide Sb2(S, Se)3 semiconductor is regarded as one of the most promising photovoltaic materials due to their high optical absorbance coefficient and tunable band gaps. However, current researchers rarely optimize experimental conditions based on characteristics of the Se/S ratio in Sb2(S, Se)3 material and ignore the experimental optimization based on material characteristics. Herein, Sb2(S, Se)3 thin films with three different Se/(Se + S) ratios (Se = 0.2, 0.5, 0.8) are prepared by vapor transport deposition (VTD) based on the temperature sensitivity of the evaporator source. The influence of VTD conditions of Sb2(S, Se)3 on optical properties, electrical properties, film quality, and defect characteristics are investigated through UV absorbance spectra, current density versus voltage (J-V) measurements, scanning electron microscopy (SEM), deep-level transient spectroscopy (DLTS), respectively. It is concluded that the deposition temperature is closely associated with the shift of the band gap. Moreover, different original Se/(Se + S) ratios yield different optimum temperatures (Se = 0.2, 480 °C; Se = 0.5, 500 °C; Se = 0.8, 520 °C), and optimum temperature increase with Se atom ratios. With optimization of the Se/(Se + S) ratio and deposition temperature, a Sb2(S, Se)3 solar cell (Se = 0.8) prepared under 520 °C has optimal light absorbance, longer carrier lifetime, and better film quality, displaying a high efficiency of 6.78%.

Bio-functionalization, stabilization and potential functionalities of hyaluronate macromolecules capped copper oxide nanoparticles

The optical-electrical properties of CuO-NPs (copper oxide nanoparticles) are being expanded widely for high-technological uses. In accordance with the idea of an eco-friendly synthesis process, CuO-NPs were synthesized utilizing a safer method; stabilized by biopolymer sodium hyaluronate (SH) rather than a hazardous substance. Using one variable at one time method with constant reaction variables, the synthesis parameters were optimized and the characteristics of CuO-NPs were controlled. The resulting particles exhibited restricted distribution, were typically round or oval in form and particle size of 17 ± 1.3 nm (by TEM and SEM), strongly crystalline (by XRD) and were noticeably stable. The experimental analysis of FT-IR documented that the redox reaction between biopolymers and metal cations; coupled by capping effect of thin layer of SH-macromolecules, are primarily responsible for the formation and stabilization of CuO-NPs. Also, CuO-NPs exhibited strong bactericidal (ZOI 22–27 nm; antibiofilm potential 71–85%), anti-diabetic (70–72%), DNA cleavage and antioxidant activity (70–85%). Additionally, SH-stabilized CuO-NPs demonstrated catalytic activity for the reduction of catalytic dyes, degrading at a rate of over 91–93% in about 10–20 min. The current synthetic technique may be applied consecutively to synthesize catalytically active CuO-NPs which exhibited remarkable in-vitro biological and biomedical capabilities, possessing the potential to be exploited as a broad-based agent in a variety of biomedical and industrial processes, including the treatment of wastewater.

(Invited) Macroscopically Aligned Carbon Nanotubes for Photonics, Electronics, and Thermoelectrics

The remarkable flexibility, stable chemical structure, and extraordinary thermal, electrical, and optical properties of carbon nanotubes (CNTs) are promising for a variety of applications in flexible and/or high-temperature electronics, optoelectronics, and thermoelectrics, including wearables, refractory photonics, and waste heat harvesting. However, the long-standing goal in the preparation of CNT ensembles is how to maintain the extraordinary properties of individual CNTs on a macroscopic scale. The polydispersity and randomness remain two main challenges. Here, we will discuss different methods for creating macroscopically aligned CNTs, including spontaneous formation of wafer-scale aligned CNT films via controlled vacuum filtration and production of ultrahigh-conductivity CNT fibers and films through solution spinning and coating. We will then describe the optical, dc and ac electrical, thermal, and thermoelectric properties of these materials. These results are promising for device applications in various fields such as flexible CNT broadband detectors, spectrally selective thermal emitters, and thermoelectric devices.

Temperature-dependent electrical resistivity of tungsten oxide thin films

Tungsten oxide (WO3) thin films have been previously investigated for various applications. Optoelectronic and electrochromic applications require detailed knowledge of the electrical properties of such films, whereas gas-sensing applications require understanding the electrical resistivity and its variation with temperature. In numerous studies on the electrical properties of WO3 thin films, the results were widely scattered and critically dependent on deposition and resistivity measurement conditions. This paper presents a systematic investigation of the electrical resistivity of WO3 thin films and its variation with temperature. WO3 thin films were deposited on heated substrates using thermal evaporation both in vacuum and under an oxygen atmosphere. Subsequently, the films were annealed in air or in vacuum. The structural, chemical, optical, and room-temperature electrical properties were measured. The temperature-dependent electrical resistivity was measured at 300–700 K in air or in vacuum. The activation energies for electrical conduction were derived from these measurements and were used to investigate the mechanisms responsible for electrical conduction.

Strategies for fourfold enhancement of narrowband green AC-driven electroluminescence from zinc gallate co-doped with Ce3+ and Mn2+ ions by field-enhanced energy transfer

The alternating current (AC)-driven metal-oxide-semiconductor (MOS) structured electroluminescent (EL) devices currently received great attention and are continuously developed due to low-voltage system requirements compared to conventional thin-film EL devices. They shared great advantages of facile fabrication and low power consumption. However, they are not ready for commercial use due to inadequate optical performance. To resolve this issue, this paper presents three enhancement strategies of the narrowband green emission of MOS-EL device on a silicon substrate, which results from the 4T1 → 6A1 transition of the dopants from ZnGa2O4:Mn2+, Ce3+ emitting layer by effective energy transfer from the blue emission of Ce3+ to the green emission of Mn2+ under high electric field. The concentrations of Mn2+ and Ce3+ co-dopants (1), and the annealing temperatures (2) are optimized, and the electrical-optical properties with varying voltage and frequency (3) are investigated. As a result, our MOS EL device generates a large surface-emission EL light with a fourfold-enhanced EL performance. In summary, this research offers a new strategy to resolve the insufficient performance of MOS-EL devices with promising optical properties.

The Role of Annealing Treatment on Crystallographic, Optical, and Electrical Features of Bi2O3 Thin Films Prepared Using Reactive Plasma Sputtering Technology

Bismuth oxide (Bi2O3) has attracted considerable research interest in test thin films made utilizing the reactive plasma sputtering (RPS) technology-assisted annealing treatment, allowing the development of diverse BixOx thin films. SEM, phase X-ray diffraction patterns, UV-Vis spectrometers, and D.C. two-probes are used to identify the crystallographic structure and assess the films’ optical-electrical properties. The XRD examination showed that forming Bi2O3 films with an amorphous to multiphase crystalline structure for sputtering time of 40 min was due to soda glass substrate temperature at a range of 30–35°C. Thin films of Bi2O3 crystal structures improved with annealing heat treatment at 200, 300, 400, and 500°C. Yet the formation of crystalline phase (β-Bi2O3 with δ-Bi2O3) Bi2O3 nanostructures occurred at higher temperatures. SEM images showed transparent particles highly affected by annealing temperatures. The nanostructures were about 102–510 nm long, and the diameter was 50–100 nm. The Bi2O3 film optical band gaps and nanostructures ranged from 2.75 to 3.05 eV. The annealing temperature differences affected the crystallite sizes, optical band gaps, and surface roughness. The findings showed that these differences caused the phase transition in Bi2O3 structures. The electrical calculation revealed that the electrical conductivity improved with annealing temperatures of 150–250°C while declining with temperature (300–500)°C with typical semiconductor films.