Thickness Dependence of Cu-layer-based Transparent Heaters

Transparent conducting electrodes attract attention in relation to solar cells, touch panels, displays, e‐readers, and transparent heaters. In many cases, rarefied metal nets with optical transmittance of ≈90% and with minimal sheet resistance are sought after. Here, a mesh of conducting polymer nanofibers is developed as a transparent conducting electrode. A sheet resistance of 8.4 kΩ sq−1 with 84% optical transmittance is achieved with polyethylene oxide/poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate (PEO/PEDOT:PSS) blended polymer nanofibers. This study also demonstrates that such nanofiber being deposited on a glass substrate can be used as a transparent film heater in relevant applications such as window heating or displays at harsh environments. Such a transparent heater is rated at 0.41 W in.−2 for 120 V. It is also capable of heating a substrate up to ≈70 °C in 4 min at 60 V from room temperature without any degeneration of nanofiber network, rendering itself as a practically useful transparent heater. The performance of the PEO/PEDOT:PSS nanofiber‐coated transparent glass heater is comparable to that of the relatively expensive indium tin oxide thin‐film heaters.

Transparent planar layer copper heaters for wearable electronics

Transparent heaters are gaining significant attention for applications such as antifog glass, smart windows, and smart farm greenhouses. A transparent heater basically consists of transparent conducting materials that serve as a heating area and contact pad electrode to apply power. To fabricate a transparent heater, materials with excellent light transmittance and low sheet resistance are required. Among various transparent conducting materials, such as Indium Tin Oxide (ITO), carbon nanotube (CNT), graphene, and silver nanowires (AgNWs), AgNWs are particularly favored due to their good electrical, optical, and mechanical properties. However, in order to improve the heating characteristics of transparent heaters, research is essential not only on improving the properties of transparent conducting materials but also on the design of contact pad electrodes that can uniformly improve current distribution. Here, we explore various shapes of contact pad electrodes for AgNW-based transparent heaters to improve current distribution. Shapes such as line, spot, twisted, and parallel-type contact pad electrodes are designed and investigated to optimize overall heating characteristics. We analyze the heating properties of these transparent heaters with various contact pad electrodes, demonstrating how their specific shape and size affect heating characteristics and uniformity. We also investigate the optimal shape of the contact pad electrode to minimize transmission loss through UV-VIS spectroscopy. As a result, we confirm that the shape of the contact pad electrode was important for simultaneously achieving high heating characteristics of 120 °C, good heating uniformity, and over 80% transparency in an AgNW-based transparent heater.

For electric vehicle application, one of the problems to be solved is defrosting or defogging a windshield or a side mirror without gas-fired heaters. In this paper, we report on a high performance of transparent heater with meshed amorphous-SiInZnO (SIZO)/ Ag/ amorphous-SiInZnO (SIZO) (SAS) for pure electric vehicles. We have adopted amorphous oxide materials like SIZO since SIZO is well known amorphous oxide materials showing high transparency and smooth surface roughness. With the mesh processing technology, a transparent electrode with high transmittance of 91% and low sheet resistance of 13.8 Ω/ϒ was implemented. When a 10 V supply voltage is applied to transparent heater, the transparent heater on glass substrate was heated up to 130oC in just 5 seconds and then reached to 250oC after tens of seconds due to the low sheet resistance. In addition, the SAS transparent meshed heater (TMH) showed high stability under cycling test and long time working stability test.

Thickness dependence of superconductivity for In/Mo thin films

In this study, a series of optimization steps were performed in the production of Al-doped ZnO (AZO) thin films to tailor their properties as efficient transparent heaters and for near-infrared (NIR) reflectance. The films were produced on 50 × 75 mm2 glass substrates via magnetron sputtering and capped with a protective SiO2 layer. Processing parameters such as deposition temperature, film thickness, and annealing conditions were all optimized in terms of structure, morphology, optical/electrical properties, and heating/deicing behavior. Electro-thermal characteristics of the films were investigated using a thermal imaging infrared camera under various input voltages. The optimized AZO/SiO2 coatings displayed impressive room-temperature electrical conductivity (σ) of nearly 3774 S/cm with a sheet resistance (Rs) of 3.53 Ω/□, carrier concentration (η) of 1.14 × 1021, and Hall mobility (µ) of 20.48 cm2/Vs. These films exhibited very high optical transmittance (above 96%) in the visible range and reflectance (73% at 2500 nm) in the NIR region. The highest figure of merit (FOM) was achieved as 237 (× 10–3 Ω−1). Deicing tests were performed with samples cooled to − 40 °C and resulted with complete removal of ice/water only within 3 min. In addition, the heater exhibited a high surface temperature of 161 °C (12 V), a good thermal resistance value (219 °C cm2/Watts) with stable and reversible heating behavior. More importantly, these results reveal the potential of optimized AZO/SiO2 coatings as alternatives to transparent tin-doped indium oxide heaters and NIR reflecting mirrors for vehicular applications.

We present the scalable fabrication of a novel transparent heater (TH) architecture by continuously creating metallic micromesh patterns on a flexible substrate via Photo Roll Lithography (PRL). The optimal TH structure is explored by systematically investigating the heating and transmittance characteristics depending on the metal material, thickness, and micromesh dimension. The transmittance is further enhanced by incorporating the biomimetic moth-eye anti-reflection layer (ARC) which effectively reduces the reflection along with diffraction and scattering of incident light. The fabricated ARC-integrated TH exhibits an excellent transmittance with satisfactory heating up to 47.5oC at the applied current of 0.6 A, which demonstrates ten times more power-efficient than conventional macroscale wire defrosters used in most vehicles. Successful defrosting of both planar and curved large-area surfaces is visually demonstrated by attaching the 70 × 70 mm-sized THs fabricated on a glass or flexible polymer. This versatile, highthroughput TH architecturing may be applicable to many other devices requiring flexibility, scalability, and power-efficient operation, and their commercially-feasible production.

We have observed the increase in sheet resistance with the lapse of time for some Al0.3Ga0.7N/GaN HEMT structure wafers, and this was due to the decrease in electron mobility rather than the decrease in carrier concentration. In the wafers, a lot of triangular micro-cracks extending to 〈110〉 directions were observed by AFM, which were a few tiny lines initially. On the other hand, a wafer that was kept in the nitrogen atmosphere was little increased in sheet resistance. It is plausible that oxygen decreases surface energy of cleaved planes, and micro-cracks progress. The reciprocal lattice map of XRD showed no lattice relaxation of the AlGaN/GaN system. Monochromatic CL image of 359 nm wavelength showed those micro-cracks as dark lines, which means that the micro-cracks work as non-radiative centers, and the charge of trapped electrons might deplete or scatter 2DEG beneath the micro-cracks and cause the increase in sheet resistance. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Determination of W-Ti/Al thin-film interaction by sheet resistance measurement

Transparent conducting electrodes (TCEs) have been made on flat, flexible, and curved surfaces, following a crack template method in which a desired surface was uniformly spray-coated with a crackle precursor (CP) and metal (Ag) was deposited by vacuum evaporation. An acrylic resin (CP1) and a SiO2 nanoparticle-based dispersion (CP2) derived from commercial products served as CPs to produce U-shaped cracks in highly interconnected networks. The crack width and the density could be controlled by varying the spray conditions, resulting in varying template thicknesses. By depositing Ag in the crack regions of the templates, we have successfully produced Ag wire network TCEs on flat-flexible PET sheets, cylindrical glass tube, flask and lens surface with transmittance up to 86%, sheet resistance below 11 Ω/□ for electrothermal application. When used as a transparent heater by joule heating of the Ag network, AgCP1 and AgCP2 on PET showed high thermal resistance values of 515 and 409 °C cm(2)/W, respectively, with fast response (<20 s), requiring only low voltages (<5 V) to achieve uniform temperatures of ∼100 °C across large areas. Similar was the performance of the transparent heater on curved glass surfaces. Spray coating in the context of crack template is a powerful method for producing transparent heaters, which is shown for the first time in this work. AgCP1 with an invisible wire network is suited for use in proximity while AgCP2 wire network is ideal for use in large area displays viewed from a distance. Both exhibited excellent defrosting performance, even at cryogenic temperatures.

a‐Si:H thin films‐based solar cells offer the benefit of reducing material consumption and fabrication costs. However, such thin absorbing layer reduces the photovoltaic efficiency, due to their poor light absorption at red and near‐infrared wavelengths. Metal NPs such as silver (Ag) can exhibit strong localized surface plasmon (LSP) resonances at different wavelength ranges, allowing increasing the light absorption in the active layer. The goal of this study is to perform an optimal structure of Ag NPs allowing to optimize the light absorption within the a‐Si:H solar cells by means of scattering. Ag layers are deposited on two different SnO2 substrates (with different roughness). After annealing, quasi‐spherical shaped of Ag NPs with diameters ranging from 10 to 130 nm are obtained. UV‐visible spectroscopy displays one LSP resonance around 560 nm with the less rough substrate, while three LSP resonances around 560, 700, and 850 nm are observed with roughest substrate. These differences are mainly due to the size distribution of NPs and underline the strong influence of the surface roughness and the coupling effect on the NPs behavior. a‐Si:H thin film solar cells with Ag NPs are subsequently elaborated. Spectral response shows an improvement of about 14–15%.

Ti-based metal-organic frameworks (MOFs) are demonstrated as promising photosensitizers for photoelectrochemical (PEC) water splitting. Photocurrents of TiO2 nano wire photoelectrodes can be improved under visible light through sensitization with aminated Ti-based MOFs. As a host, other sensitizers or catalysts such as Au nanoparticles can be incorporated into the MOF layer thus further improving the PEC water splitting efficiency.

Anomalous electrical conductivity change in MoS2 during the transition from the amorphous to crystalline phase

Transparent and flexible polytetrafluoroethylene (PTFE) thin film passivation for ITO/AgPdCu (APC)/ITO (IAI) electrodes is developed to prevent severe degradation and maintain the reliable performance of the flexible IAI electrodes. Also, oxygen ion beam treatment (IBT) on the surface of the IAI electrode improves the adhesion between the top ITO and PTFE passivation layer, as well as the performance of the passivation layer. The IAI electrode with PTFE passivation exhibits constant sheet resistance, transmittance, and flexibility, even after the 85 °C and 85% RH test. However, the bare IAI electrode shows a significant increase in sheet resistance and a decrease in transmittance and flexibility, owing to the incorporation of moisture and impurities into the IAI layer, and agglomeration of the APC layer. To demonstrate the feasibility of PTFE passivation, the performance of flexible and transparent thin film heaters (TFHs) with the bare IAI and PTEF/IAI samples are compared. The better stability and reliability of the PTFE/IAI‐based TFHs than the bare IAI‐based TFHs indicate that the PTFE film effectively prevents the introduction of moisture and impurities. The performance of the TFH with PTFE/IAI electrode implies that sputtered PTFE film is a promising transparent and flexible thin film passivation for high‐quality oxide‐metal‐oxide multilayer electrodes.

Multilayer polymeric nanocomposite thin film heater and electromagnetic interference shield