Innovation in electronic materials: Creating novel devices with new functionalities
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Introduction In the past, materials have been developed much earlier than devices that have been applied later. After scientists discovered new materials and defined the basic principles of their synthesis, they found applications in devices that eventually became products. For example, we know that liquid crystals were discovered in 1888,1 but it was about 80 years before RCA produced the first liquid-crystal display (LCD), and Sharp did not introduce the first LCD product until 1975. Thirty years later, in 2005, Samsung commenced mass production of larger sized (82 in.) thin-film transistor (TFT) LCDs (Figure 1). The realization of LCD devices was thus the result of utilizing new functionalities of evolutionary liquid-crystal materials. Lithium batteries followed a similar development. Lithium cobalt oxide was invented by Metalloy in 1946, who filed the first patent on this material. However, the first lithiumion battery was not developed until 1979 at Oxford University, and another 20 years passed before Sony introduced the first product in the market in 1991.2 Since that time, these batteries have evolved as a power source for smartphones, laptops, and even for plug-in hybrid vehicles or for pure electric vehicles (Figure 2). In the past, materials have been discovered before an application was found. At the beginning of the analog era, when cathode ray tubes were introduced, cathodoluminescent materials were already available. However, when the 3G era
began in 2000, the evolution of display devices was very fast, and the customers for these devices became demanding; materials were therefore developed to fulfill their requirements. Many highly efficient phosphor materials are available today, but we would like to increase their efficiency; however, we lack deep blue phosphorescent materials. This means that device market requirements are currently somewhat ahead of materials development. In the case of quantum dot (QD) lightemitting diode (LED) materials, we are working very hard to develop highly efficient, low cost, environmentally friendly QD materials, but such devices are already required by the market. The development of electrolytes has been important for use in batteries. For heavy duty applications or analog devices such as portable devices, aqueous electrolytes (acid or alkaline electrolytes) can be applied such as in lead acid, nickel cadmium, or nickel metal hydride batteries. Since the invention of the lithium-ion battery, they were applied to smartphones, even in electric vehicles, and now we are trying to develop smaller wearable devices. However, development of electrolyte systems, including cathode and anode active materials, still lags behind customer demand for increased energy density, which is directly related to the operating time and driving range of electric vehicles. The life cycle of devices is currently much faster than that of materials. Moore’s law states that transistor density doubles and cost is halved every two years. The first lithium-ion battery
Hyuk Chang, Materials Research Center, SAI
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