High‐Performance Transparent Electrodes for Automobile Windshield Heaters Prepared by Combining Metal Grids and Oxide/Metal/Oxide Transparent Electrodes

Abstract

One of the most promising applications of TCEs is a large-area transparent heater on the front window in automobiles, which allows convenient removal of fog on the indoor side of the windshield and frost on its outdoor surface. Considering that windshield fogging frequently occurs during driving, convenient way of fog removal on windshield can be directly related with safety of the people on board. Moreover, recent trend in the increasing demand of electrical automobiles is expected to generate a huge market for TCE technology, since electrical automobiles do not come with the air-blowing system, which is used in defogging and defrosting on windshield. Generally, it is understood that the critical technology in transparent heater is to achieve ultralow sheet resistance below 0.5 Ω □ −1 , while keeping the transmittance over 70% at the same time. Since the voltage of automobile batteries ranges only 12 to 16 V, the area of the most automobile windshields is over 1.0 m 2 and the gap between electrodes is over 700 mm, [3] achieving low-enough sheet resistance to be viable for real application is understood to be a difficult mission. As far as we have done searches in the related fields, no TCEs have been developed that can satisfy all those specifications at the same time. [2] Up until now, indium-tin oxide (ITO) has been most widely used in TCE industry. However, even with high optical transmittance reaching 90%, ITO has not been successful in application for automobile windshield due to relatively high sheet resistance (10 to 100 Ω □ −1 ). [4][5][6] Recent need for TCE technology introduced three different candidate materials including carbon-based materials, metal nanowires (NWs), and metal grids. Although carbon-based materials including carbon nanotubes (CNTs) [7][8][9][10][11] and graphene [12][13][14] has some advantage in flexibility, CNTs and graphenes have relatively high sheet resistance and low optical clarity compared with ITO. Among metal NWs, [15][16][17][18][19][20][21] silver nanowires (Ag NWs) have been improved greatly in recent years with their sheet resistance reaching around 30 Ω □ −1 , while keeping the transmittance up to 90%. However, a severe optical problem like "haze" Transparent heaters can be fabricated with a wide variety of materials including indium-tin oxide, carbon nano tubes, graphenes, metal nanowires, metal grids, and hybrid-type electrodes. However these materials have been applied to small area heaters below 0.01 m 2 because of the limit of electrical and optical properties. High-performance transparent electrodes for large-area purpose (over 1.0 m 2 ) have never been developed with any practical applicability in spite of their utility for removing fog or iced water on automobile windshield, which can be critical for safety and convenience of the drivers. Achieving ultralow resistance with high transparence is the major technical barrier in windshield heaters due to the intrinsic long distance between electrodes and low battery voltage in automobiles. In this study, a high per...

The Transmittance Modulation of ZnO/Cu/ZnO Transparent Conductive Electrodes Prepared on Glass Substrates

“…The TCE electrodes having excellent transparency and conductivity can also be used as high-performance transparent heaters for various applications, either as an integrated component for optoelectronic devices e.g., for the removal of snow on solar panels [ 22 ] or as a stand-alone defrosting device, e.g., for vehicles and windows [ 23 , 24 ]. Figure 5 a shows the heater characteristics for the ZnO/Cu/ZnO electrodes having 6 nm-, 8 nm-, and 10 nm-thick Cu layers.…”

Fabrication of High‐Performance Silver Mesh for Transparent Glass Heaters via Electric‐Field‐Driven Microscale 3D Printing and UV‐Assisted Microtransfer

“…The front windshield of an automobile has minimal transparency and haze requirements of T > 70% and H < 1%, respectively. The low voltage ( V ≤ 12 V) and high power ( P ≥ 100 W) requirements make the manufacturing of low R s heaters particularly difficult . As such, the results presented in this study are particularly promising for applications to automobiles, aircraft, ships, and outdoor displays because of the demonstrated performance, cost‐efficiency, and low power consumption.…”

“…Transparent glass heaters (TGHs), one of the most widely used and promising transparent heaters (THs), exhibit tremendous applications in many occasions including vehicle windows, outdoor displays, heat retaining windows, solar voltaic cells, mirrors, and camera lenses . Although the indium tin oxide (ITO) has been the most commonly used transparent conductive film (TCF) for the THs, the brittleness, fragile ceramic nature, and harsh processing conditions of the ITO and the scarcity of the indium limit the further application for the THs . As such, recent studies have proposed several emerging materials for the next‐generation TCF to replace ITO, including carbon‐based materials, metal nanowires (NWs) or nanofibers (NFs), metal meshes, conductive polymers, and hybrid materials .…”

“…The R s of carbon‐based materials and conductive polymers is higher than that of ITO, which restricts their use in high‐performance TGHs . Metal NWs or NFs and metal meshes have been studied extensively in recent years and have been described as the most promising TCF materials due to excellent electrical and optical properties (in some cases superior to ITO).…”

“…However, the preparation of high‐performance metal mesh with T > 90% and R s < 0.5 Ω sq −1 has rarely been reported and is difficult to achieve . To improve the photoelectric properties of metal meshes, Cheong et al demonstrated a method for producing high‐performance heaters for automobile windshields with R s = 0.1–0.3 Ω sq −1 at T = 82% by combining metal grids and oxide/metal/oxide transparent electrodes . Han et al developed a new flexible device with R s = 0.1–0.4 Ω sq −1 at T = 86–96% using a molding and electroplating process .…”