Next generation e-paper is very thin and needs little electricity

A Swedish research group has developed electronic paper that is very thin and yet has very good properties. This makes it suitable for a large number of applications.

Researchers at Chalmers University of Technology in Sweden have invented a new method for reflective displays, also called e-papers or E-Ink are designated. Although it also uses ambient light to save electricity and enables super-thin displays, it also offers a high level of color brilliance that was previously unheard of. In contrast to the LCD / LED method in particular, the new structure of the electronic paper requires extremely little electricity and still shows a bright display. Such displays are conceivable as advertising posters, in e-readers and other devices on which users want to read for a long time, with little fatigue and in an energy-saving manner. Further advantages of e-paper: low weight, high flexibility and optimal readability even in difficult lighting conditions. The Chemists published their results recently in Nano Letters magazine.

Disadvantages of e-paper eliminated

E-papers work with a passive display. In contrast to LED technologies, it does not have to continuously switch on lighting elements in order to represent something. This has a strong effect on energy consumption and has other advantages: With reflective displays, the viewing angle is irrelevant and the contrast is also good outside in sunlight. But there was always one problem: the colors were not of high quality. For this reason, many e-readers do not display any colors at all. That could change now. PhD student Marika Gugole from the chemistry faculty explains the task: “In order for reflective screens to compete with the energy-intensive digital screens that we use today, the images and colors must be reproduced with the same high quality. That will be the real breakthrough. “

In addition to the new chemistry, the scientists also relied on a rearrangement of the nano-layers in order to brighten the image. (Graphic: Nano Lett. 2021, 21, 10, 4343-4350)

Pure color representation as with the LED

Chemists at Chalmers University had already managed to display the same amount of colors as with LEDs. They succeeded in doing this using inorganic nanostructures based on tungsten trioxide (WO3), which is already used in “intelligent windows”. However, the image quality suffered. The problem: Many subpixels were necessary for a good display, which e-paper technology achieves with semitransparent counter-electrodes. However, the more of them are used, the more the overall reflection decreases: the display becomes darker and darker. So the group was looking for a method that could display more colors so that you don’t have to use so many reflection-reducing electrodes for subpixels. The first solution was to use a thin film of platinum as a mirror. This achieved a wide range of colors and a high degree of reflection. More importantly, the solution allowed them to change the shift order. They place the electrochemical cells behind the reflective surface and thus avoid the reduction in reflection from the electrodes. The result: bright, high-resolution display with crisp colors. The energy consumption is almost zero because the ambient light is used, the authors explain.

Production could be done within months

Head of research Andreas Dahlin can imagine an industrial solution in a very short time. He is certain: “A large industrial company with the appropriate technical competence could in principle start developing a product with the new technology within a few months.” In addition to smartphones, tablets and outdoor advertising, he is also used in mobile digital screens in front.

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