Average Optical Transparency Research Articles

Impact of oxygen vacancy on luminescence properties of dysprosium-doped zinc oxide thin films

Pristine and dysprosium-doped ZnO thin films, highly c-axis oriented, were grown on a c-Al2O3 substrate using the pulsed laser deposition technique. During the deposition process, the growth was impacted by changes in the oxygen partial pressure. The structural, optical, and compositional properties of the pristine and dysprosium-doped ZnO thin films were systematically characterized using various state-of-the-art experimental techniques. The crystallinity associated with these films was observed to be highly dependent on the oxygen partial pressure maintained during the growth process. An average optical transparency of more than ∼90% in the visible spectral range (i.e., 400–800 nm) was observed for all specimens. For doped specimens, expected intra-4fn emissions of (dysprosium) Dy3+ ions that emanated from the 4F9/2 energy state were observed in room-temperature photoluminescence spectra under direct excitation. The Jacobian-transformed wavelength-to-energy plot for Dy-doped ZnO thin films in the UV-Visible region revealed intriguing findings. Specifically, it depicted a prominent peak at 2.82 eV, indicative of the energy state of Dy3+ ions, alongside intense band-edge emission and various defect-related emissions. The intensity of these transitions was observed to depend on the oxygen partial pressure kept during deposition. An x-ray photoelectron spectroscopy analysis of the doped specimen confirmed the +3 oxidation state of dysprosium into the ZnO matrix. These results provide a promising approach for controlling the doping and growth strategy of Dy-doped ZnO thin films, thereby opening up a wide range of applications and enhancement for next-generation optoelectronic devices.

Tungsten Oxide Thin Films for Electrochromic Applications: Pulse Width‐Controlled Deposition by High‐Power Impulse Magnetron Sputtering

Tungsten oxide (WO3) thin films have been of prime interest among electrochromic materials because of their chemical stability, strong adherence to various substrates, and high coloration efficiency. High‐power impulse magnetron sputtering (HiPIMS) holds great potential in fabricating durable WO3‐based electrochromic layers. However, the tungsten target–plasma interactions in reactive‐HiPIMS deposition of WO3 and their role in modulating the electrochromic function of the resulting WO3 coatings are yet to be understood. Herein, by controlling the HiPIMS pulse length, the stoichiometry of tungsten oxide structures can be tuned to optimize the transparency and electrochromic function of the coatings. X‐ray photoelectron spectroscopy data shows that at pulse lengths shorter than 85 μs, the concentration of suboxide compounds is less than that of tungsten trioxide, while for pulse lengths longer than 100 μs, this balance is reversed. The average optical transparency of the coatings in the range of visible light is higher than 80%. The optical transmittance modulation (ΔT) of 38.1, 36.2, and 34.3% and coloration efficiency of 41.3, 38.4, and 35.9 cm2 C−1 are measured for the WOx samples deposited at pulse lengths of 70, 85, and 100 μs, respectively. Tuning the HiPIMS pulse characteristics is a simple strategy to deposit tungsten oxide films with tuned electrochromic properties for an array of applications, from smart windows to wearable displays.

Transparent and Flexible Patch Antenna Using MMF for Conformal WiFi-6E Applications

In this paper, a patch antenna with compact, flexible, and transparent properties is presented to support Wi-Fi 6E (2.4 GHz/ 6 GHz) applications. This antenna design was formulated based on a transparent metal mesh film (MMF), for which the average optical transparency (OT<sub>av</sub>) is 69% and the sheet resistance (R<sub>s</sub>) is 0.1Ω/sq. The measurement results on frequency bands of 2.4-2.51 GHz and 5.87-7.04 GHz show that the average gain exceeds 5.4 dBi and 6.3 dBi with corresponding radiation efficiency rates as high as 67.8% and 70%. In addition, for the purpose of integration into aesthetic devices for smart home applications, the antenna conformed to foam and a lamp. All research outcomes here indicate that the proposed antenna maintains a directional radiation pattern, as well as transparency and flexibility, making it a potential candidate for transparent Internet of Things (IoT) applications.

Tailoring the Emission Behavior of WO3 Thin Films by Eu3+ Ions for Light-Emitting Applications

The article reports the successful fabrication of Eu3+-doped WO3 thin films via the radio-frequency magnetron sputtering (RFMS) technique. To our knowledge, this is the first study showing the tunable visible emission (blue to bluish red) from a WO3:Eu3+ thin film system using RFMS. X-ray diffractograms revealed that the crystalline nature of these thin films increased upto 3 wt% of the Eu3+ concentration. The diffraction peaks in the crystalline films are matched well with the monoclinic crystalline phase of WO3, but for all the films', micro-Raman spectra detected bands related to WO3 monoclinic phase. Vibrational and surface studies reveal the amorphous/semi-crystalline behavior of the 10 wt% Eu3+-doped sample. Valence state determination shows the trivalent state of Eu ions in doped films. In the 400-900 nm regions, the fabricated thin films show an average optical transparency of ~51-85%. Moreover, the band gap energy gradually reduces from 2.95 to 2.49 eV, with an enhancement of the Eu3+-doping content. The doped films, except the one at a higher doping concentration (10 wt%), show unique emissions of Eu3+ ions, besides the band edge emission of WO3. With an enhancement of the Eu3+ content, the concentration quenching process of the Eu3+ ions' emission intensities is visible. The variation in CIE chromaticity coordinates suggest that the overall emission color can be altered from blue to bluish red by changing the Eu3+ ion concentration.

Photolithographic Transparent Flexible Graphene Oxide/PEDOT:PSS Electrode Array for Conformal Organic Transistor

A facile and damage-free patterning pro- cess was proposed to solve the incompatibility in the traditional photolithography process by introducing graphene oxide (GO) as a protective layer for poly (3,4-ethylenedioxythiophene): polystyrene (PEDOT:PSS) film. As a result, a high-resolution GO/PEDOT:PSS elec- trode array with a feature size down to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3 ~\mu \text{m}$ </tex-math></inline-formula> was fabricated. Moreover, the PEDOT:PSS films exhibit average optical transparency up to 92.6% in the visible light range, excellent conductivity (~2000 S cm−1), and high conformability. Based on the GO/PEDOT:PSS electrode array, the confor- mal organic field-effect transistors with the highest mobility of up to 1.4 cm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{{2}}\,\,\text{V}^{-{1}}\,\,\text{s}^{-{1}}$ </tex-math></inline-formula> and average mobility of 0.83 cm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\vphantom {\text {D}^{\text {j}}}{2}}\,\,\text{V}^{-{1}}\,\,\text{s}^{-{1}}$ </tex-math></inline-formula> by layer-by-layer lamination were successfully fabricated. Our process was highly compatible with traditional photolithographic patterning techniques, which may provide a route for the integration of complex soft electronics.

Optically Transparent Patch Antennas Using Saltwater for WLAN Applications

This paper presents the design, fabrication, and measurement of a novel transparent patch antenna using saltwater with high-opticaltransparency applications for wireless local area networks (WLANs) at 2.4–2.5 GHz. The most important reason for using saltwater for transparent antenna applications is its superior average optical transparency (OTav &gt;90%) compared to other typical transparent electrodes, such as indium tin oxide (ITO; OTav &gt;80%) or metal-mesh film (MMF; OTav &gt;60%). This study designs three types of antennas: an antenna with a conductive part made of copper sheet (CS) for both the radiator and ground plane (case 1) to compare the performance with two types of proposed transparent antennas that use saltwater as the conductive parts; an antenna with saltwater for the radiator and MMF for the ground plane (case 2); and an antenna with saltwater for both the radiator and ground plane (case 3). The case 1, case 2, and case 3 antennas have peak gains of 6.87, 4.4, and 1.91 dB, respectively, and have corresponding radiation efficiencies of 93.5%, 62%, and 34%. To the best of our knowledge, this is the first demonstration of a transparent patch antenna using saltwater.

Effect of Gd doping on spray pyrolyzed NiO thin films for optoelectronic applications

In the present work, we systematically investigated the effect of Gd (1, 3, and 5%) doping on the structural, morphological, electrical, and optical properties of NiO thin films deposited on glass substrate using the spray pyrolysis method. X-ray diffraction study revealed that the deposited Gd:NiO(0–5%) films exhibit cubic structure with preferred orientation along (111) direction. The average crystallite size decreases from 15 nm to 12 nm with increasing Gd doping concentration. The atomic force microscope (AFM) topography study revealed that there is a decrease in grain size and variation of roughness with increasing Gd content into NiO lattice . The energy-dispersive X-ray spectroscopy (EDX)/ scanning electron microscope (SEM) mapping studies show the presence and uniform distribution of Gd in the Gd:NiO films. The average optical transparency (70%) and the optical band gap energy values decrease in Gd doped NiO films. The refractive index values are found to be in the range of 1.5–2.6. The higher values of linear and nonlinear optical parameters like χ1, χ3 and n2 are found to be 0.98 esu, 3.31 × 10−10 esu and 2.92 × 10−9 esu, respectively in Gd doped NiO films. The current study indicates that the Gd doping concentration has a strong influence on linear and non-linear optical properties of NiO films and makes them useful in several optoelectronic device applications.

Mo/W/Al doped tin oxide thin films: exploring optical and mechanical properties for transparent protective coating applications

For the last few years research has been intensified in exploring and improving mechanical properties of tin oxide thin films besides the optical and electrical ones that enhances the film's functionality and broadens its application purview. The present investigation reports a comprehensive study on the effect of Mo, W, and Al doping on optoelectronic and mechanical properties of tin oxide thin films. The films exhibited an optical transparency over 350–400 nm with an average transmission of 85–98% at 550 nm and mechanical hardness spanning over 2–8 GPa, and electrically resistivity in the range 900–200 Ωm, based on the dopant used and its content. Compared to bare tin oxide film, the doped films exhibited a decrease in optical transparency with an improvement in the hardness. 10 wt.% Mo doped tin oxide film exhibited good average optical transparency 72% at 550 nm, highest elastic recovery of 70%, highest hardness 8.0 ± 0.5 GPa and reduced-modulus of 89 ± 0.5 GPa of all the films. The investigation demonstrates a simple technique of producing mechanically hard tin oxide thin films useful as transparent protective coatings.

Planar Saltwater Analysis for Transparent Electromagnetic Shielding Applications

Optically transparent electromagnetic applications, such as EMC windows, require high optical transparency (OT) while maintaining good electrical performance which is difficult to achieve with conventional transparent electrodes (TEs). In this paper, we proposed a novel planar saltwater as a solution to overcome the difficulty. The electrical and optical characterizations of the planar saltwater are experimentally investigated with good agreement to theoretical prediction. The saltwater has a high average OT of 91.8% which is highest among conventional TEs. Moreover, the planar saltwater shows a shielding effectiveness (SE) above 22 dB with only 3 mm of thickness in the C-band. The SE can be significantly improved by an increase in the thickness of planar saltwater. Along with other advantages of cheap, safe, easy access, and flexible performance, the saltwater can be considered as a potential candidate for transparent electromagnetic shielding applications.

Superstrate-type flexible and bifacial Cu(In,Ga)Se2 thin-film solar cells with In2O3:SnO2 back contact

Bifacial and flexible Cu(In,Ga)Se2 (CIGS) thin-film solar cells with superstrate-type structure were fabricated. For this fabrication, the substrate-type solar cells were first transferred from Mo/Glass substrates to 50-µm-thick flexible fluorinated ethylene propylene (FEP) copolymer films as superstrates using a lift-off process. The 300-nm-thick In2O3:SnO2 (ITO) thin-films were subsequently deposited on the rear sides of the CIGS absorber layers as back contacts (BC) of the finished bifacial devices with the structure of FEP/Epoxy/Al/Ni/Zn0.9Mg0.1O:Al/Zn0.8Mg0.2O/CdS/CIGS/ITO/Ni/Al. Particular attention was paid to maintain the high optical and electrical transport properties of ITO-BC as well as to improve the Ohmic-like contact behavior at the CIGS/ITO interface to improve cell performances. Under the optimized ITO preparation, the resulting ITO thin film possesses the average optical transparency of ITO (>77%) in the wavelength range of 400–1100 nm, and the resistivity of 6.1 × 10−4 Ωcm with corresponding high carrier mobility of 42.8 cm2/Vs, as well as Ohmic-like characteristics at the CIGS/ITO interface can be realized with shunt resistance as low as 5.5 Ωcm2. Consequently, the flexible and bifacial CIGS thin-film solar cell was fabricated with efficiencies of 9.1% and 2.4% for frontside and backside illuminations, respectively. In this study, highly transparent and conductive ITO thin films have been successfully used as BC in flexible and bifacial CIGS solar cells.

Characterization of oxygen vacancy effect on structure and optoelectronic properties of sol gel deposited Zn2-xCaxSnO4 nanostructured films

Zinc stannate (ZTO) is considered as potentially transparent semiconducting material due to high visible transparency and electrical conductivity for transparent electronics and barrier layers. In the present work, the structure-property relationship for spin coated Zn2-xCaxSnO4 (0.0 ≤ x ≤ 0.2) nanostructured films using acetylacetone as sol gel precursor solvent was investigated. The crystal structure, molecular structure, surface morphology, chemical state, optical and electrical properties were evaluated. X-ray diffraction study confirms polycrystalline films with inverse spinel structure. The formation of additional vibrational modes in the Raman spectra confirms Ca dopant incorporation in ZTO system. X-ray photoelectron spectroscopy spectra show an enhancement in oxygen vacancy contribution and Sn2+ contributions as compared to otherwise stable Sn4+ state with Ca content. An improved average optical transparency (81.9%) in visible spectrum along with highest carrier concentration (3.7 × 1020 cm−3) gives maximum Haache's figure of merit value of 1.45 × 10−4/Ω for sol-gel derived Zn1·95Ca0·05SnO4 nanostructured films, confirms its suitability as transparent conductor.

Multi-Spectral Metasurface With High Optical Transparency, Low Infrared Surface Emissivity, and Wideband Microwave Absorption

In this paper, we propose the design of a multi-spectral metasurface(MSM) which can simultaneously achieve quite good optical transparency, low infrared emissivity and wideband microwave absorption. To this end, optically transparent materials were used in the MSM design, including indium tin oxide, Polyethylene terephthalate and polymethyl methacrylate. The MSM is composed of three functional layers: a frequency selective surface (FSS) on the top, a resistively absorbing layer in the middle and a complete conducting sheet at the bottom. Due to large occupation ratio (OR) of conducting area and the low-pass property of the FSS, electromagnetic waves are allowed to penetrate through it into the middle absorbing layer, simultaneously with low surface infrared emissivity. A prototype was designed, fabricated and measured. Both the simulation and experiment results show that the MSM can achieve strong absorption over 90% in 12.03- 29.43GHz and low IR emissivity about 0.3 in 3.0-14.0μm simultaneously. Moreover, the average optical transparency is higher than 90%. Due to the excellent multispectral compatibility, the MSM may find applications in electromagnetic protection, stealth technologies, etc.

Highly Transparent Planar Dipole Using Liquid Ionized Salt Water Under Surface Tension Condition for UHD TV Applications

In this article, a feasibility study on an optically transparent planar dipole antenna using liquid salt water at wide ultra-high frequency (UHF) band (470-771 MHz) for application in external antenna of ultra-high-definition television (UHD TV) is presented. The most significant reason behind using liquid salt water for transparent antenna applications is its excellent average optical transparency (OTav) (>95% at salinity of 40 ppt) compared with other typical solid transparent thin-film electrodes such as indium tin oxide (>73%) or multilayer films (>78%). Each conductive arm of the proposed dipole is constructed from a salt-water layer held between two clear planar acrylic layers (ε <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> = 2.61, tan δ = 0.01, OT <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">av</sub> > 90%) (acrylic/salt water/acrylic; ASA) due to surface tension. To investigate the electrical and optical properties of the ASA structure, we analyze the surface tension to determine the thickness of the salt-water layer that finalizes its sheet resistance and OT <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">av</sub> . The average gain and efficiency of the antenna are 1.72 dBi and 74%, respectively, in the operating UHF band. This makes the proposed antenna a good candidate for application as a transparent external antenna in UHD TVs and proves that it is possible to use salt water for high-frequency devices.

Room temperature deposition of high figure of merit p-type transparent conducting Cu–Zn–S thin films and their application in organic solar cells as an efficient hole transport layer

High figure-of-merit p-type transparent conducting Cu–Zn–S thin films with Zn doped CuS structure were successfully deposited by Successive Ionic Layer Adsorption and Reaction (SILAR) method at room temperature. Films were deposited with an optimal Cu:Zn:S ratio of 75:25:50 in the precursor solution. The thickness of the films was controlled by varying the number of deposition cycles. The composition, structure, morphology, electrical, electronic and optical properties of the as deposited films were studied in detail. All the films exhibited relatively high conductivity and transparency resulting in high figure-of-merit values. Overall, the hole concentration and conductivity are in the range of degenerately doped semiconductors. The Cu–Zn–S film deposited with 40 nm thickness has an electrical conductivity of more than 1000 S/cm and average optical transparency greater than 81% in the visible region. These values are higher than most of the other reported p-type transparent conducting materials, especially for room temperature deposition. Conventional bulk heterojunction organic solar cells were fabricated with structure ITO/Cu–Zn–S/P3HT:PC71BM/ZnO/Al, where Cu–Zn–S is the hole transport layer. The best configuration resulted in an efficiency of 1.87% suggests the suitability of Cu–Zn–S thin films as a hole transport layer in organic solar cells.

Fabrication and Characterisation of ZnO Thin Film by Sol–Gel Technique

Abstract We investigated the structural and optical properties of zinc oxide (ZnO) thin film as the n-type semiconductor. In this work, the sol–gel method used to fabricate ZnO thin film on glass substrate with 0.5 mol/l of zinc acetate dehydrates. The crystals quality of the thin film analyzed by X-ray diffraction and the optical transmittance was carried out by an ultraviolet-visible spectrophotometer. The DRX analyses indicated that ZnO film have polycrystalline nature and hexagonal wurtzite structure with (002) preferential orientation and the measured average crystallite size of ZnO of 207.9 nm. The thin film exhibit average optical transparency about 90 %, in the visible region, found that optical band gap energy was 3.282 eV, the Urbach energy also was calculated from optical transmittance to optimal value is 196.7 meV.

Production and examination of ZnO thin film for first time using green synthesized method from aqueous Citrus reticulata peel extract

In the present work, we report, for the first time, the production of nanostructured ZnO thin films using green synthesized (GS) ZnO nanoparticles (NPs) by spray pyrolysis system. The effects of the deposition amount on the optical, electrical and structural properties of the ZnO thin films were investigated. The ZnO-NPs were synthesized using a Zn(Ac)2.2H2O solution in an aqueous extract of Citrus reticulata peel. The morphologies of the GS samples were characterized by FE-SEM and the crystal structures were identified by XRD analysis. As the deposition amount increased from 5 to 20 mg the average crystallite size increased from 44 to 81 nm. The deposition amount and deposition time significantly affected the crystal type end size. The UV–visible spectrum showed that the average optical transparency was higher than 85%. The electrical conductivity values significant changed with the crystal quality and morphology.

High Optical Visibility and Shielding Effectiveness Metal Mesh Film for Microwave Oven Application

A typical microwave oven generates an electromagnetic wave in an ISM band of 2.45 GHz. To prevent this unwanted microwave leakage through its front door, a circular perforated metal sheet is typically used with low shielding effectiveness (<; 27 dB) and with poor visibility (<; 50%) which is usually difficult to check the progress of cooking. In this paper, we investigate sheet resistance (R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</sub> ) and optical transparency (OT) for electrical and optical performance of two transparent electrodes (TEs) including metal mesh film (MMF) and indium tin oxide (ITO) and compare those to the currently used perforated copper sheet (PCS) in commercial microwave oven. The measured RS and average OT in visible spectrum of MMF is 0.11 Ω/sq and 68.4%, and its figure of merit (FoM) is 203.8 which is the highest among them. The measured shielding effectiveness of MMF, ITO, and PCS at 2.45 GHz are 31.4, 21.0, and 25.5 dB, respectively. The results indicate that MMF has highest FoM and the best EMC performance among the TEs and PCS, which makes it the most suitable candidate for microwave ovens.

Abrasion resistant semitransparent self-cleaning coatings based on porous silica microspheres and polydimethylsiloxane

Transparent, abrasion-resistant and superhydrophobic coatings have attracted considerable interest owing to their great advantages in applications. In this work, a semitransparent abrasion-resistant superhydrophobic coating was attained via depositing suspensions of porous silica microspheres and polydimethylsiloxane, followed by calcining and fluorating process. Herein, the porous silica microspheres were fabricated through a template method. Consequently, the coating exhibited a water contact angle of 153°, a hexane contact angle of 100° and an average optical transparency of 78%. Significantly, the coating displayed a robust resistance against sandpaper abrasion and knife-scratch. Furthermore, the coating also exhibited excellent self-cleaning performance even after it was contaminated by oil.

Investigation of structural, optical and electrical properties of ZnS thin films prepared by ultrasonic spray technique for photovoltaic applications

ZnS films have important applications in photovoltaic devices. In the current study, the ZnS films were deposited by ultrasonic spray method on heated glass substrate at temperature equal to 450°C.In this article, we report the effect of deposition time on the different structural, optical and electrical properties of ZnS. All the samples obtained were treated using X-ray diffraction (XRD), optical transmittance spectroscopy (UV-V) and four-point method. The results of X-rays diffraction showed that the deposited material was pure zinc sulfide having a cubic sphalerite structure with preferential orientation along the (111) direction. As well the grain size was around 38–102nm, when the deposition time increases. The transmittance measurements exhibit an average optical transparency between 35 and 75% in the visible range (400–750nm) for different deposition times. The direct band gap energy for all films was calculated and found to be from 3.48 to 3.92eV. The films' thickness is increased with deposition time from 195nm to 1756nm. The electric resistivity of the deposited film varies also with the deposition time between 1.51×105 and 20.84×105Ω.cm.

Green synthesis and antimicrobial activity of ZnO nanostructures Punica granatum shell extract

Abstract The manufacture of nanoparticles (NPs) is a new area of investigation due to potential applications related to the improvement of new technologies; in particular, environmentally safe manufactured nanomaterials have become a growing area within nanoscience. In this research, we synthesized zinc oxide (ZnO)-NPs using an aqueous extract of Punica granatum shell prepared using the green synthesis method. The ZnO-NPs were examined by X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM) and UV-visible spectroscopy. The XRD patterns illustrated a single phase hexagonal (wurtzite) structure. The FE-SEM micrographs revealed the formation of erythrocyte-like structures and the average particle sizes were found to be 30–180 nm. The UV-visible measurements showed that the average optical transparency is over 85% in the visible range. The electrical conductivity values of the nanostructured ZnO-NPs were between 7.07×10−7 and 3.31×10−4 Ω−1 cm−1 in the temperature range 25–650°C. In addition, the ZnO-NPs did not show any antimicrobial affect against a Gram-positive bacterium (Bacillus thuringiensis).