High Visible Light Transmittance Research Articles

Research progress and device applications of multifunctional materials based on two-dimensional film/ferroelectrics heterostructures

With the rapid development of microelectronic integration technology, the miniaturization, integration and multifunction of electronic devices are becoming a general trend. Two-dimensional materials are a class of layered material with atomic layer thickness, and have unique electrical, magnetic, optical and mechanical properties. The co-existence of the weak van der Waals force between layers and the strong covalent bonding within layers makes the two-dimensional material very suitable for the miniature design of new-generation multifunctional electronic devices. Two-dimensional materials, represented by graphene and transition metal chalcogenides, exhibit high mobility, adjustable energy band and high visible light transmittance, and thus having become the frontier hotspots in the field of micro-nanoscience in recent years. Synergy between two-dimensional materials and various functional materials such as SiO<sub>2</sub> insulator, semiconductor, metal and organic compound may lead to new properties and device applications, thus can deepen and expand the basic research and application of two-dimensional materials. Among them, ferroelectric materials have received much attention because of their spontaneous polarizations, high dielectric constants, and high piezoelectric coefficients. The two-dimensional ferroelectric composites well have the advantages of the two, i.e. they not only contain a variety of rich phenomena such as the magnetoelectric coupling effect, ferroelectric field effect and lattice strain effect, tunneling effect, photoelectric effect, and photoluminescence effect, but also have broad applications in devices such as multi-state memories, tunneling transistors, photoelectric diodes, solar cells, super capacitors, and pyroelectric infrared detectors, which have attracted wide concern from academia and industry. To better understand the combination of two-dimensional thin films with ferroelectric substrates and provide a holistic view, we review the researches of several typical two-dimensional film/ferroelectrics heterostructures in this article. First, two-dimensional materials and ferroelectric materials are introduced. Then, the physical mechanism at the interface is briefly illustrated. After that, several typical two-dimensional film/ferroelectrics heterostructures are mainly introduced. The ferroelectric materials including Pb(Zr<sub>1–<i>x</i></sub>Ti<i><sub>x</sub></i>)O<sub>3</sub>, (1–<i>x</i>)PbMg<sub>1/3</sub>Nb<sub>2/3</sub>O<sub>3</sub>–<i>x</i>PbTiO<sub>3</sub>, P(VDF-TrFE), are mainly summarized, and other ferroelectric materials such as P(VDF-TrFE-CFE), BaTiO<sub>3</sub>, BiFeO<sub>3</sub>, PbTiO<sub>3</sub>, CuInP<sub>2</sub>S<sub>6</sub>, HfO<sub>2</sub> are briefly involved. The future research emphasis of the two-dimensional materials/ferroelectrics composites is also suggested at the end of the article. This review will present a significant reference to the future design of miniature and multifunctional devices.

Bulk preparation of transparent IGZO TFTs with CS gate dielectric as glucose sensor on a pilot line

In this paper, the indium gallium zinc oxide (IGZO) thin-film transistors (TFTs) with chitosan (CS) gate dielectric are prepared by the conventional photolithography technique on a pilot line. As-prepared devices on 200 × 200 mm substrate is very uniform, and have good performance of high on/off drain current ratio ~ 10−6, low subthreshold swing ~ 0.24, low-threshold voltage ~ 0.20 V and high-visible light transmittance > 90%. The glucose oxidase is drop-cased on the CS gate dielectric surfaces to make fully transparent CS-based IGZO TFTs with sensitivity to glucose. It is found that the current noticeably changes with increasing glucose concentrations. Herein, the glucose detection range from 0.5 to 30 mM covers the normal range of human blood glucose concentration. Moreover, the response time for glucose sensing is < 10 s, which is effective in detecting glucose. The results suggest that the CS-based IGZO TFTs can be used to detect glucose and provides a simple process to achieve low-cost- and larger-area fabrication of biosensors.

Formation and properties of ZrO2–Cu composite nanoglass films

Unlike conventional amorphous materials without grain boundaries and dislocations, nanoglasses consist of amorphous nanoparticles and glass-glass interfaces, which results in unique properties. In this work, we have developed a ZrO2–Cu composite nanoglass by multi-target magnetron co-sputtering, and its microstructure, optical and electrical properties have been studied by using aberration-corrected transmission electron microscope, spectroscopic ellipsometry, UV–Visible spectrophotometer and Hall measurements. It is found that Cu is enriched into the amorphous interfacial region. The ZrO2–Cu composite nanoglass shows high visible light transmittance (over 70%), high refractive index (1.98–2.08) and large optical band gap (5.0–5.7 eV). As the Cu content increases, the electrical properties are also improved. The enrichment of Cu at the interface further provides a new route for the preparation of 2D nano-conducting networks.

Near infrared radiation shielding using CsxWO3 nanoparticles for infrared mini light-emitting diodes

Recently, near infrared LEDs have been used in small electronic devices due to the trend of manufacturing compact systems. The intensity of near infrared (NIR) optical device needs to be moderated if the chip emits too much power. In tradition, color pigments are used as additives in the encapsulant of LEDs to reduce the intensity of over irradiated NIR, a strategy which results in unaesthetic appearance. Cesium doped tungsten trioxide (CsxWO3) nanoparticles (NPs) have good near infrared absorption ability. Applying very few amount of CsxWO3 NPs into the encapsulation materials of NIR optical device can decrease NIR intensity while still maintain high visible light transmittance without losing aesthetic touch of those devices such as LED transmitters. The addition of only 0.0021 wt% CsxWO3/PMA dispersion in epoxy encapsulant can drop 15.5% NIR (860 nm) intensity but barely reduce visible light (only 3.2% at 450 nm). The excellent performance of CsxWO3 NPs; i.e., good NIR absorption and visible light transmission properties, can be suitable for maintaining the moderate luminescence intensity of small optoelectronic devices like NIR mini- or micro- light-emitting diodes.

UV-shielding alginate films crosslinked with Fe3+ containing EDTA

In this study, we fabricated a soft, transparent UV-shielding film (Alg-Fe3+-EDTA) by crosslinking sodium alginate with a ferric ion solution containing EDTA. The obtained films were characterized via SEM, ATR-FTIR, XRD, TG and DTG; the results indicated that the synergistic gelation of ferric alginate and alginic acid existed in Alg-Fe3+-EDTA film. The Alg-Fe3+-EDTA film performance to be optimized under the following conditions: 1.6% Fe3+, 0.8% EDTA, and crosslinking duration of 12 min. The Alg-Fe3+-EDTA film had high visible light transmittance, the UV-C (200–280 nm) and UV-B (280–315 nm) shielding rates were 100%, and the UV-A (315–400 nm) shielding rate was 98.37%; the UPF reached 50+; additionally, the tensile strength and elongation-at-break were 56.85 MPa and 10.45%, respectively, and still have ultraviolet shielding effect under water environments or after strong light irradiation. This work provides an efficient method to improve the optical and mechanical ability of ferric alginate films.

Facile fabrication of hydrophobic polyvinylpolysilsesquioxane aerogels with improved optical properties

Optically transparent and mechanically enhanced aerogels are promising nanoscale materials for thermally insulating window glazing. However, there still exists a longstanding challenge for silica aerogels to realize the combination of optical and mechanical properties. Here, we present a facile synthetic means towards hydrophobic polyvinylpolysilsesquioxane (PVPSQ) aerogels with improved optical properties, originating from polyvinyltrimethoxysilane polymers in ethanol−water medium. The as-prepared PVPSQ aerogels with surface hydrophobicity modification show high water contact angle of 124 ± 5°. Benefiting from the homogenous networks acquired in the ethanol−water solvent, hydrophobic PVPSQ aerogels have a huge surface area of 1106 ± 50 m2/g and a high visible-light transmittance of 92.3% at 550 nm wavelength. Moreover, monolithic PVPSQ aerogels with doubly cross-linked nanostructure exhibit excellent mechanical property and thermally insulating capacity. The compressive strength with 20% strain is 0.71 MPa, and the thermal conductivity of typical sample is 0.0271 W/(m·K) in ambient environments. All these results will be meaningful for the design and industrial production of transparent insulating materials.

Highly (4 0 0) preferential ITO thin film prepared by DC sputtering with excellent conductivity and infrared reflectivity

ITO (Indium Tin Oxide) thin film with a sandwich structure that comprises two layers of oxygen-poor layer and an oxygen-rich layer was deposited on glass substrates by DC sputtering using a ceramic target. The effect of structure on the photoelectric properties of the ITO thin film was investigated. The results indicated that the as-prepared ITO film with sandwich structure showed high (4 0 0) preferred orientation. Simultaneously, the ITO thin film with sandwich structure exhibited excellent optoelectronic properties, which has a low resistivity of 1.384 × 10−4 Ωcm, high visible light transmittance of 88.34% and a high IR reflectivity of 88.37%. Excellent optoelectronic properties can meet the infrared stealth requirements for aircraft windows.

A flame‐retardant DOPO‐MgAl‐LDH was prepared and applied in poly (methyl methacrylate) resin

A novel inorganic and organic composite flame retardant (9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide [DOPO]–layered double hydroxide [LDH]) was synthesized via grafting DOPO with organic‐modified Mg/Al‐LDH, which was introduced into poly (methyl methacrylate) (PMMA) resin to prepare the flame‐retardant PMMA composites. Thermogravimetric analyzer (TGA) showed that the T‐50% of DOPO‐LDH/PMMA composites enhanced by about 20°C, and with the 20% flame retardant, the residual char content can be increased by 39.8% in the air atmosphere compared with LDH/PMMA composites. In the UL‐94 and the limiting oxygen index (LOI) tests, it can be found that compared with LDH/PMMA composites, the LOI value of DOPO‐LDH/PMMA composites were raised evidently with the increased flame retardants, and the droplet combustion was greatly improved. These results could be ascribed to the action of DOPO free‐radical, catalytic charring of polymer and the effect of LDH physical barrier. Moreover, the novel DOPO‐LDH not only given PMMA a good flame‐retardant property and thermal stability, but also have higher visible light transmittance, ultraviolet‐shielding effect, and low loss of mechanical properties, which could further facilitate the wide application of inorganic environment‐friendly flame retardants in general resins and engineering resins and broaden the application of polymers.

Thermally-induced cellulose nanofibril films with near-complete ultraviolet-blocking and improved water resistance

In recent years, ultraviolet (UV) protection films made from cellulose nanofibril (CNF) have drawn significant attention, owing to its high transparency, high mechanical strength and relatively high thermostability. Generally, CNF films had poor UV-shielding performance, and required UV absorbent to enhance their UV-shielding ability. Herein, a simple thermal treatment is proposed to directly improve the UV blocking properties of CNF films without incorporating UV absorbent. After thermal treatment at 160 °C, the CNF films exhibited a near-complete UV blocking ability. In particular, they exhibited full absorption of ultraviolet A (UVA) and ultraviolet B (UVB), and also showed a high visible light transmittance of 72%. In addition, the UV-shielding films performed stable UV-blocking when exposed to UV irradiation. Simultaneously, the hornification induced by thermal treatment endowed an improved hydrophobicity for CNF films. However, the tensile strength of the CNF films decreased from 133 MPa to 81 MPa after thermal treatment at 160 °C.

Direct spray-coating of highly robust and transparent Ag nanowires for energy saving windows

A large portion of energy consumed in buildings via infrared (IR) radiation through windows, therefore, IR blocking protection or low-emission (Low-E) window is urgently required for more energy-saving buildings. While most Low-E glass require complex and high-cost vacuum sputtering coatings, IR blocking layer that can be directly coated with cost-effective and large-scale process is desired. Herein, we report facile and scalable processing of silver nanowires/polyvinyl butyral (AgNWs/PVB) coatings for high performance Low-E windows. The spay process can be applied to create reliable IR modulation layer directly onto normal glass, and have also been expanded to roll-to-roll coating on flexible plastics. The AgNWs/PVB coating showed high transmittance of visible light (∼83.0%), high reflectivity of mid-IR (∼69.8%), low emissivity, as well as reliable chemical and mechanical durability.

The effects of surface plasmon resonance coupling effect on the solar energy modulation under high transmittance of VO2 nanostructure

Improving solar energy modulation ability while maintaining high visible-light transmittance has been a challenge of VO2 application in smart window. The improvement of solar modulation ability will often be accompanied by the decrease of visible light transmittance. In the present work, we propose a solution to improve the solar energy modulation ability and maintain high visible-light transmittance through etching the sputtered VO2 thin film by dilute sulfuric acid, which is based on the strong resonance coupling effect. We prepared planar VO2 thin film and acid-treated film with the similar transmittance. Their transmittances (Tlum) are about 57%. However, the solar energy modulation rate (ΔTsol) of acid-treated VO2 particles is increased by 277.8% compared with planar VO2 film. FDTD method is used to calculate the optical properties of acid-treated and planar VO2 film, the simulation results are consistent with experimental results. The increment of ΔTsol is related to the surface plasmon resonance and its coupled electromagnetic field of metallic state VO2. These results demonstrate that surface plasmon resonance and its coupling effect can be used to further enhance the solar energy modulation while maintaining the visible light transmittance. We hope these results will contribute to the area of smart window and other fields.

Flexible and colorless shape memory polyimide films with high visible light transmittance and high transition temperature

Colorless shape memory polyimide (CSMPI) has potential applications in broad fields, especially in advanced optoelectronics due to the excellent optical transparency, shape memory effect and high temperature resistance. In this work, high flexible dianhydrides and fluorine-containing diamines were used to synthesize CSMPI, which simultaneously combined great shape memory performance with high optical transparency. The effects of monomer ratios and imidization temperatures on the molecular structure and properties were investigated. Moreover, the CSMPI film possesses a higher glass transition temperature (Tg) of 234 °C, compared with the reported transparent shape memory polymers. Most importantly, the transmittance of CSMPI film is 87%–90% at 450–800 nm, meeting the requirements of heat resistance and transmittance of the substrate. Both shape recovery and shape fixity are over 97%. Flexible and colorless CSMPI films severed as substrates provide more potential in optoelectronic devices such as OLED and OPV, etc.

A novel method to improve phase transition of VO2 thermochromic films by Cs0.32WO3 nanoparticles

The VO2/Cs0.32WO3 composite thermochromic films were designed to promote the practical application of the VO2-based smart windows. The addition of 0.9 wt% Cs0.32WO3 can significantly shorten the phase transition response time and improve the solar heat shielding capacity of VO2, while maintaining high visible light transmittance (49.6%) and good solar modulation ability (10.4%). Furthermore, the phase transition of the composite film can occur at indoor temperature of 30 °C, and the indoor temperature can be greatly reduced by 7.7 °C under the simulated solar irradiation. These excellent properties make the VO2/Cs0.32WO3 films promising as smart energy-saving windows.

The effect of post annealing temperature on grain size of indium-tin-oxide for optical and electrical properties improvement

Abstract Background (Problem) Indium tin oxide (ITO) is a transparent conductive oxide (TCO) thin film used as a transparent electrode. Given its high demand for the manufacture of transparent electrodes (high visible light transmittance, low resistance) in applications such as liquid crystal displays, touch screens, light emitting devices and solar cells, ITO thin films have attracted immense research interest. Objectives This study determines the effect of grain size on the optical and electrical properties of the ITO thin films under different annealing temperatures. Materials and methods ITO thin film was deposited at room temperature by a high frequency magnetron sputtering method using a target composed of In2O3 and SnO2. The structural, optical and electrical properties of the thin films annealed at 250 °C, 350 °C, 450 °C and 550 °C for 1 h were then analyzed. Results The research shows the grain size of indium-tin oxide thin films is strongly related to annealing conditions. The grain size was found to increase with increasing annealing temperature, although the crystal structure did not change for all the samples. It was observed that the lowest resistivity (500 × 10−4 Ω-cm) and highest optical transmittances (90–98%) of ITO films were obtained at annealing temperature of 450 °C. At low annealing temperatures, the measured resistivity is dependent on the effect of grain size, where it decreases with increasing grain size. Conclusion This work showed that the grain size of ITO thin films is strongly influenced by post annealing technique and conditions applied, thus providing a tool for enhancing the optical and electrical properties of the film.

Investigation of properties of transparent and conducting V-doped Ga2O3 films

V-doped Ga2O3 films were prepared by using radio frequency (RF) magnetron sputtering method with different substrate temperature. The influence of substrate temperature on the properties of V-doped Ga2O3 films was investigated. The results indicated that the crystalline quality of the films increases significantly with increasing substrate temperature. All films showed a smooth surface and high visible light transmission. As the substrate temperature increased, the optical band gap of the films decreased slightly and the resistivity decreased drastically. XPS spectra revealed the valence state of V dopant in the films and two binding energies corresponding to V4+ and V5+ ions were obtained.

Investigation of structural and magnetic properties of Co+ ion implanted indium tin oxide thin films on polyethylene terephthalate (C10H8O4)n substrates by 100 keV ions

Indium Tin Oxide (ITO) thin films have been used extensively in many applications, such as solar cells. In particular, ITO has been the material of choice in flat panel displays as one of its electrodes due to its low resistivity, high transmission of visible light and high free carrier density that contributes to its relatively low electrical resistivity. Modification of ITO thin films on polymer substrates using transition metal ion beams is rarely reported in literature. In this work, ITO thin film samples were implanted with Co+ ions of energy 100 keV at fluences 1 × 1014, 1 × 1015 and 1 × 1016 ions/cm2. The grain sizes of the ITO thin films were observed to increase with increase in ion fluence, showing that the quality of the ITO thin films and crystallinity were getting enhanced. At a fluence of 1 × 1016 ions/cm2, a high value of 2.33 × 10−3 emu/g magnetization was estimated. The level of residual magnetism in the Co+ implanted thin films increased at an average of 35% with increase in ion fluence. This means that Co+ implanted ITO thin films have good ability to retain a certain amount of residual magnetic field at zero magnetizing, as the ion fluence increases. Furthermore, the Co+ ion implanted ITO thin films were found to exhibit clear room temperature ferromagnetism. The shift in hysteresis loops along applied magnetic field axes provides information about the exchange bias of Co+ ion implanted ITO thin films in relation to grain size.

Assembly of shell/core CDs@CaF2 nanocomposites to endow polymers with multifunctional properties

The shell/core structure of CDs@CaF2 nanocomposites (CCNCs) were prepared by assembling fluorescent carbon dots (CDs) inside the inorganic CaF2 substrates using co-precipitation interaction. CDs endow CaF2 with properties of good UV-absorbing behavior and efficient blue light emission instead of rare-earth such as Eu that is expensive and susceptible to polluting the environment during the mining process. Due to the nanometer size and surface effect of nano CaF2, and the approximate refractive index between CaF2 and polyethylene (PE), CCNC/PE film exhibits better elongation at the break than pure PE film while maintaining high transparency and visible light transmittance. Simultaneously, the CCNC/PE film was experimentally demonstrated to have outstanding performance of anti-UV and blue light conversion, which shows that CCNCs can be a novel and promising multifunctional additive applied in polymers especially for greenhouse film.

Cinnamate‐Functionalized Cellulose Nanocrystals as UV‐Shielding Nanofillers in Sunscreen and Transparent Polymer Films

AbstractSustainable and environmentally friendly UV‐shielding materials offer new opportunities in the formulation of the next generation cosmetic products. Cinnamate‐functionalized cellulose nanocrystals (Cin‐CNCs) prepared by esterifying CNCs with cinnamoyl chloride display strong UV absorption and high visible light transmittance. They are suitable for use as UV‐shielding nanofillers for sunscreen and transparent polymer films. The aqueous Cin‐CNC dispersion is waterborne, alcohol‐free, nonwhitening, waterproof, photo‐stable, and possesses a high sun protection factor (SPF). The SPF of Cin‐CNC aqueous dispersion is more than twice that of a popular commercial sunscreen at similar concentration. The Cin‐CNCs can serve as UV‐shielding and reinforcing nanofillers in hydrophilic and hydrophobic polymer matrices. The polyvinyl alcohol and polystyrene films incorporated with Cin‐CNCs display excellent UV‐shielding capacity and their Young's moduli are significantly enhanced.

Doping of aluminum (Al) into copper sulfide (CuS) nanocrystals enhanced their solar spectral selectivity

Al-CuS/PVA film possessed low NIR transmittance and high visible light transmittance. CuS nanocrystals doping Al significantly enhance their solar spectral selectivity.

Transparent energy-saving glass with high resistance to solar heat

We design and fabricate a planar energy-saving glass with high transmission of visible light and a high resistance to infrared solar heat. The proposed glass is designed by combining a photonic crystal structure made of alternating low- and high-index dielectrics and a dielectric/metal/dielectric multilayers deposited on conventional glass substrates. After delicate optimizations, a high weight-averaged transmission of infrared solar energy (17%) and low transmission of ultraviolet light (14%) is obtained while retaining over 83% transmission of visible light. As a result, we achieve a high energy-saving efficiency of 83%, which is about 30% higher than that of uncoated glass. The proposed nanofabrication-free energy-saving design is expected to have promising applications in reducing energy consumption of buildings, cars, etc.