Thanks to their thin, wheelable nature, flexible displays are finding their way into a wide range of electronics, revolutionizing portability and user experience. Self-illuminating using OLED technology and graphene, these displays offer brighter, more vibrant colors and are being used in wearable devices, smartphones with curved screens, TVs, and more. This means we can expect to see innovative products like foldable cell phones and moving newspapers in the future.
Just a few years ago, the brown tube TV at home was the only medium that delivered visual media to us. But in October 2013, Samsung launched the first foldable smartphone with a flexible display that folds 180 degrees like a man’s wallet. This technological innovation didn’t just impact the smartphone market, but also revolutionized the way various electronic devices are designed and manufactured. Unlike in the past, when only television screens could be imagined, today’s displays have been developed in a variety of forms and have become an integral part of many types of electronics. As electronics have become more portable, the question of how to make the displays that make up a large part of them thinner, lighter, and even wheelable has become a hot topic in the industry, and through much trial and error, fat displays have become flatter, thinner, and even curved. These changes revolutionize the user experience and show how advances in technology are impacting our daily lives.
As display technology evolves, flexible displays, which have only recently become commercially available, refer to any display that has curvature or can be reshaped, unlike traditional displays. Advances in this technology are opening up new possibilities in a variety of industries, paving the way for innovative products such as wearable devices to enter the market. The thickness and material of a material is important when it comes to transforming an object, as paper bends more easily than a metal plate of the same thickness, and a thin sheet of paper can be bent more easily than a thick book. Similarly, to understand how thin, wheelable materials make up a screen, we need to understand the structure of flexible displays and how they light up from within.
A big part of how flexible displays are able to wheel, as the name implies, is that they use a film that is thin enough to wheel without using glass. The film varies slightly depending on the method adopted by the company, but it usually consists of a combination of graphene and zinc oxide panels. Graphene has incredible conductivity and flexibility, making it a key material for flexible displays. Whereas glass is a hard, fragile, amorphous solid, graphene is itself a thinly stretched cross-section of graphite, which means that applying a voltage to the outside of the panel allows a large amount of current to flow through the thin device. This combination of graphene and zinc oxide panels creates a thin film that is electrically conductive.
In addition, unlike traditional LCD displays, which have a light source layer (backlight) that emits light, flexible displays use organic light-emitting diodes (OLEDs) that are self-luminous. OLED technology offers brighter, more vibrant colors and is more energy efficient, which is why it’s being adopted in more and more electronics. The basic structure of an OLED is like a sandwich: a wafer used to make semiconductors, an anode, a conductive layer that carries holes, a light-emitting layer that carries electrons, and a cathode. To explain the process of light generation, electrons from the cathode are deposited in the emissive layer, electrons from the conductive layer escape to the anode, and only holes remain. When the concentration of the remaining holes and electrons exceeds a certain level, recombination occurs between the layers, and the energy lost by the electrons during recombination is converted into light energy and light is emitted. And since the light-emitting layer is composed of different types of organic molecules, the energy lost by the electrons during recombination is different, and the relationship between the energy lost and the wavelength of the emitted light causes the light to have different colors. Using visible light as an example, the higher the energy, the smaller the wavelength of the light, resulting in a blue color, and conversely, the lower the energy, the larger the wavelength of the light, resulting in a red color. This is different from LCD displays, which display colors in proportion to the degree to which the backlight is polarized through a polarizer and filtered by an RGB (red, green, and blue, the three primary colors of light) filter. Since the light emitting entity is electrons in LEDs, flexible displays can be as thin as a sheet of paper.
The advantage of flexible displays is that they end up being portable and user-friendly. This is especially beneficial for travelers and people who often work outside. There are two main uses for bendable displays today that take advantage of these advantages. One is e-books using thin displays. You can carry a paper-thin display around with you and have access to all the books you want to read. This would save you from the hassle of having to take out course materials to take a class, as well as the cost of producing and disposing of a lot of paper. Furthermore, these displays can also contribute to environmental protection. The other is the curved screen that is inherent in electronics. Recent TVs and smartphones utilize the principle that every pixel on a large, curved screen has a relatively constant distance from the eye, allowing users to immerse themselves in the screen. This immersive experience is especially useful when playing games or watching movies. Taking the best of both worlds, we can cautiously anticipate display-based electronics that go beyond thinness and light to foldable, portable, and even bendable to allow users to view the screen at their convenience.
Inside the display, we explore how displays become thin enough to wheel and how they produce light and color. In the process, we were able to see how the technology has evolved and think about the possibilities for the future. Today, the technology is still being applied and commercialized in many electronic products, and we expect to see more display-based products on the market. In the near future, we will be carrying business card-sized cell phones in our wallets, and we will be able to read newspapers with animated shapes like in the movie ‘Harry Potter’. In this rapidly changing technology landscape, we can expect to see more innovation, and we will need to develop the ability to adapt and capitalize on it.
