QLEDs, or quantum dot light-emitting diodes, are key representatives of next-generation display technology. Quantum dots are nano-sized semiconductor crystals with unique optical properties, like tiny color magicians. When excited by electricity or light, quantum dots emit extremely pure light, and quantum dots of different sizes can emit different colors of light. This feature gives QLED a natural advantage in color performance, which can present high-purity colors that are difficult to achieve with traditional display technology, allowing us to see more realistic and vivid pictures when watching TV and using electronic devices, as if we are there.
For example, when displaying a beautiful natural scenery, the QLED screen can accurately restore the emerald green of each leaf, the delicate beauty of each flower, and the blue of the sky is more deepen and moving. Not only that, but QLED also has excellent stability, which means that it will not show significant degradation in color performance during long-term use, and will always maintain a high-quality display.
However, the development of QLED has not been without its challenges. In the preparation process, although the traditional spin coating method can produce QLED devices with good performance, this method has obvious drawbacks. It is less efficient and more expensive in large-scale production, just like customizing an item by hand, although delicate but limited in production, which greatly limits the wide application of QLED. As a result, people began to look for new preparation methods, and inkjet printing technology entered everyone's field of vision. Inkjet printing technology is like printing pictures with a printer, and quantum dot materials can be printed on the substrate according to the designed pattern, which has the potential for mass production and is relatively low-cost. However, inkjet printing also faces some problems, such as the uniformity of the printed film is not very good, which will affect the performance of the final display device.
Figure: Inkjet printing QLED: a new breakthrough in the efficiency of TV screens (Source: FOX4KC)
PTA technology breaks new ground
In order to solve the challenges faced by inkjet printing QLEDs, a research team from Nanjing University of Science and Technology, together with international partners, has developed an innovative pressure-assisted thermal annealing (PTA) technology. This technology is like finding a "magic key" for inkjet print QLEDs, opening a new door to high-performance displays.
The principle of PTA technology is actually not complicated. The researchers processed the inkjet-printed quantum dot film in a vacuum-assisted environment. In this process, they precisely control the evaporation rate of the solvent while applying a certain pressure and performing heat annealing. In this way, the quantum dots can be arranged in a more orderly manner, resulting in a smoother, more uniform film. Imagine that the original chaotic quantum dots have become neat and tidy under the influence of PTA technology, like soldiers arranged in a neat phalanx. This highly ordered quantum dot film has many unexpected benefits.
According to the data, the PTA-treated film has a rms roughness of only 0.54 nm, which is far better than the film treated by the traditional annealing method. This high uniformity greatly improves the efficiency of charge transfer in the film, reducing the generation of defects. In practical application, this advantage is vividly reflected. The red QLED prepared with PTA technology has a new record with an external quantum efficiency (EQE) of an astonishing 23.08%. And, at a brightness of 100 cd/m², it has a service life of more than 343,342 hours. The green QLED also performed well, with an EQE of 22.43% and a lifetime of more than 1,500,463 hours. This means that the display device using this QLED technology not only has vivid colors and clear picture quality, but also can work stably for a long time, which greatly extends the service life of the product.
Future outlook
The advent of PTA technology has made inkjet printing QLED technology more mature and has the potential for large-scale commercialization. It not only brings new development opportunities to the display field, but also shows broad application prospects in the fields of lighting and optoelectronics.
In the consumer electronics space, we can expect to see more products such as TVs, computer monitors, mobile phone screens, and more with inkjet printing QLED technology. These products will enter thousands of households with lower cost and higher performance, bringing better visual enjoyment to consumers. In the field of lighting, QLED lighting has the potential to become the mainstream choice of lighting in the future due to its advantages of high color reproduction and long life, making our living environment more comfortable and beautiful.
It can be said that the combination of PTA technology and QLED is a major breakthrough in the development of display technology. With the continuous improvement and development of technology, the future display world will become more exciting, bringing more unexpected surprises to our lives.
