In recent years, double-layer, high-efficiency organic electroluminescent devices (OLED) have relied on high brightness, high efficiency, wide viewing angle, autonomous light emission, all-solid-state, ultra-thin and ultra-light, simple production process, and faster response speed. Advantages, began to be widely promoted in the field of screen display. At the same time, the two major industrial fields of lighting and display have already begun to merge with each other on the research and application side, and OLED lighting has also begun to enter the daily life of the public, becoming a potential stock for the development of the lighting industry.
In the field of lighting, OLED can not only be used as indoor and outdoor general lighting, backlight and decorative lighting, but also can produce artistic flexible luminous wallpaper, monochromatic or colorful luminous windows, wearable luminous warning signs, etc. The products have broad development prospects in the lighting hotspot applications such as domestic cultural tourism night tours and smart homes.
For this reason, China Lighting Network hopes to bring new ideas that can be used for reference for the high-quality development of the national lighting industry through an inventory of a series of innovative technologies related to OLED in the world in recent years.
1. Stretchable OLED materials
In March of this year, the team of Professor Park Jinwoo of Yonsei University in South Korea produced all scalable OLED components and developed a scalable OLED material. Such materials can be applied to mobile phones whose screens can be changed in size or shape, wearable devices that are closer to the skin, and more realistic three-dimensional tactile displays.
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The material can still work stably even when it is increased to 80%, and the performance has not changed after more than 200 stretches, especially at 8V voltage which is 60% lower than the released stretch OLED.
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From a structural point of view, the material makes the substrate, anode, hole transport layer, light-emitting layer, electron transport layer, and cathode that make up the OLED all into a stretchable material. Under 60-80% tensile stress, the three primary colors RGB that make up the panel can work stably. It can also maintain stable operation when deforming the retractable OLED device with a sharp ballpoint pen core.
2. High-efficiency deep blue fluorescent OLEDs
In the same month, the Ma Dongge group of the State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, and the academician Tang Benzhong’s group conducted innovative research on this, by testing the luminescence properties and thin films of OLEDs prepared from two AIE materials with similar molecular structures. The temperature-dependent time-resolved spectra, molecular excited state energy levels, and temperature-dependent magnetic field effects of OLEDs show that the device efficiency is related to the spin conversion process between the high-level Tn and S1 in the AIE molecule, and due to the high-level triplet state and There is a competitive relationship between the internal conversion process between the triplet states and the Tn-S1 gap crossing process. Only when n is less than 4, the high-energy state Tn excitons can be effectively used, thereby achieving high efficiency.
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In the end, the research team further utilized Tn excitons of AIE materials by doping TTA upconversion materials to prepare high-efficiency deep blue fluorescent OLEDs with chromaticity coordinates CIE of (0.15, 0.08), the largest external The quantum efficiency (EQE) is 10.2%, and the maximum luminous brightness is 16817 cd/m2. The device also exhibits a low efficiency roll-off. This result lays the foundation for the further design and preparation of high-efficiency blue fluorescent OLEDs.
3. Luminous OLED "tattoo"
In February of this year, a team from University College London and the Italian Institute of Technology tried to use the light-emitting technology used in today's TVs and smartphones to bring this technology into new areas. The researchers started with an electroluminescent polymer with a thickness of only 76 nanometers and found that this polymer emits light when exposed to an electric field. On the basis of this research, the researchers applied the device to commercial tattoo paper.
The tattoo produced by this technique is only 2.3 microns thick and can be applied with the help of water and pressure just like a normal temporary tattoo. The team demonstrated by applying a green OLED tattoo on a glass plate, a plastic bottle, an orange and some paper packaging.
This tattooable OLED can be combined with other forms of tattoo electronic products to achieve light-emitting tattoos, light-emitting nails, set light-emitting signals for sweat sensors, provide light-emitting reminders for patients, light-sensitive treatments for cancer patients, and remind when fruits expire Widely used.