Five years ago, as the mainstream technology of display, the development of LCD (liquid crystal) technology showed signs of weakness. OLED is recognized as the next generation of display technology, which will be popularized in mobile phones, wearable devices, televisions, computers and other fields. However, five years later, products based on LCD technology are still the first choice of many users. OLED is mainly used in high-end products such as mobile phones and televisions, and its application level is not as expected. The reason is that the price of OLED products remains high. The price of OLED televisions of the same size is 2-3 times that of LCD televisions, which makes most users flinch. No matter how beautiful the concept is, the reality is that consumers will only buy products that are value for money and beyond value for money. If OLED technology is to become the mainstream of display technology in an all-round way, the key is to reduce the cost on the premise of ensuring efficiency and service life.
Mass production of OLED new materials is expected to significantly reduce the cost of luminescent materials
The arrival of the 5G era has outlined a bright future for people to “connect everything”. And “everything is connected” has a big premise, and the realization of “everything” needs a window for interaction. To put it more popularly, we need a “screen”, and this “screen” has huge business opportunities in the unit of hundreds of billions of dollars. However, due to different regions and different uses, display technology requirements vary. From mobile phones to televisions, from wearable devices to various household appliances, this “screen” has a product matrix covering OLED, LED, and even electronic paper and other display technologies.
In this matrix, OLED has recently become the protagonist. OLED, also known as organic light-emitting semiconductor, is widely considered as the next generation of mainstream display technology due to its characteristics of self-illumination, infinite high contrast, wide viewing angle, low power consumption, and extremely fast response. It is worth mentioning that in addition to its excellent image quality advantages, OLED can also achieve flexible appearance design of curl, transparency, folding and lightweight. By 2018, the market size of China’s OLED industry has reached US $29 billion. It is predicted that the global OLED panel shipments will reach 768 million pieces in 2019.
In view of this huge market, a research team in Guangzhou is deepening the research and development of OLED. “We focus on the research and development of new generation organic light-emitting materials and devices, including the design, synthesis and characterization of light-emitting organic molecules with adjustable excitation states, as well as their structure, electrical and photophysical properties and corresponding devices.” This is a research topic of Professor Su Shijian and his team in the State Key Laboratory of light-emitting materials and devices of South China University of Technology. I cannot understand you? In short, they are starting to research new materials to replace the existing phosphorescent OLED materials based on rare metal ligands, and can bypass the patent “moat” of European and American enterprises in this field, so as to achieve the goal of significantly reducing the production cost of OLED.
It is understood that the cost of OLED materials accounts for about 30% of the total cost of OLED screens, while OLED screens are only one of the many parts of the whole product. “Once there is a breakthrough in the performance of new materials and mass production, it is expected to reduce the cost of OLED luminescent materials to only 10% of the current level. This may not have a great impact on reducing the price of OLED screen phones, but it will have a significant impact on the television industry.” Professor Su Shijian said.
The reporter interviewed 20 citizens who bought TV in a home appliance market in Guangzhou. Without exception, OLED TV is their first choice. Ms. Ma, a citizen, told the reporter that if the OLED TV could get a 70% discount, she would buy it. The price of a 65-inch LCD TV of the same brand is 7999 yuan. A small survey by reporters found that the premium range of OLED technology that consumers are willing to accept is between 20% and 30%.
Because this new technology based on new materials is still in the laboratory stage, from the laboratory to the production line, it also needs to go through complicated and complicated processes, and needs the close cooperation of “production, education and research”, and there are still many uncertainties. Therefore, it is difficult to assess how much the technology will reduce OLED TV after it is put into production. However, one thing is certain that the price of OLED TV will not be as high as it is now, and it will appear in front of consumers at a more affordable price.
Expect to achieve breakthroughs in material innovation within five years
The story of Edison’s invention of electric light is familiar to everyone. He has classified and tested more than 1600 different heat-resistant materials. In fact, there is no shortcut to invention, but to try and make mistakes. Through trial and error again and again, the unsuitable materials are eliminated, and the rest is suitable. To some extent, Professor Su Shijian and his team are also doing what Edison did. The difference is that the verification process of OLED materials is more complicated, lengthy and rigorous.
Professor Su Shijian told reporters that the quantum efficiency per unit of organic light emitting devices can be easily achieved by pure organic light emitting devices without rare metals, and the efficiency is the same as that of rare metals. “The challenge now * is that in terms of service life, only when the service life reaches the same level as that of rare metal phosphors, and they are truly put on the market, can they be accepted by consumers.”
At present, the team is testing and debugging more than 20 kinds of pure organic light-emitting materials and trying different new methods. When can we make a breakthrough? When answering this question, Su Shijian thought for nearly ten seconds before giving a prediction that he thought was more responsible: he hoped that within five years, one or two new materials would emerge and realize mass production. It can be understood that any kind of R&D innovation may make a breakthrough in the next second, but it may also be 10 or 20 years later.
TADF – OLED is a hot candidate for OLED
It is understood that the research team has made many achievements in the research and development of improving the efficiency of organic light emitting devices. The R&D personnel have made every effort to develop thermal activation delayed fluorescence materials (TADF) and high-efficiency OLED devices that are feasible for evaporation and solution processing. Researchers have successfully applied thioanthracene oxide to the field of organic optoelectronics and used it as an electron acceptor. With benzene ring as the connecting bridge and acridine and phenoxazine as the electron donors, they have designed and developed new thermal activation delayed fluorescence (TADF) materials ACRDSO2 and PXZDSO2 that can be applied to both evaporation and solution processing processes. The external quantum efficiency of the green light evaporation device based on ACRDSO2 reaches 19.2%, while the solution processing device without hole transport layer can also achieve 17.5% of the external quantum efficiency. Compared with the classical green light TADF material 4CzIPN, the solution processing device has greatly improved both the driving voltage and the external quantum efficiency.
It is reported that compared with the phosphorescent materials containing rare metals that are mainly used in commercial OLED panels at present, pure organic luminescent materials with thermal activation delayed fluorescence (TADF) characteristics are a potential material that can achieve exciton utilization and low cost advantages. At present, TADF-OLED has been able to achieve the same electroluminescent performance as OLED based on phosphorescent materials, and has become a hot candidate for realizing the application of low-cost and high-efficiency OLED technology.
At the same time, the R&D team designed a new type of trispiro-ring donor unit, and combined with the classic triazine receptor, successfully prepared a blue-light TADF material with high efficiency and multi-function, Tspiro-S-TRZ. Compared with the acridine receptor units with non-spiral and bispiral structures, the long-rod-like, strongly rigid, and large steric steric hindrance trispiral units can form a longer molecular skeleton and form a bispiral non-conjugate structure. This work provides an efficient and multifunctional blue light TADF material design idea.
Test material of luminous material, try to use virtual simulation technology
In the process of new material development, efficiency and service life testing are the most time-consuming links, both of which are indispensable. Because the new materials need to be matched with devices, and the structure of devices is diverse, so it is necessary to conduct adaptability tests on different devices. It seems that the test work is not complicated, but the temperature, load, structure, electricity and so on all need to be tested. Each item is like embroidery, which is a very detailed and time-consuming work, with a large workload.
In order to improve the R&D rate, on October 10, this year, the laboratory of Susijian cooperated with the Dutch simulation software company Simbeyond to establish the OLED simulation modeling partnership. Simbeyond has a set of software called Bumblebee, which can specially optimize the simulation of molecular scale photoelectric processes in disordered systems (such as OLED organic light emitting devices, OPV organic photovoltaic devices, OFET organic transistors, etc.).
The intuitive user interface of Bumblebee enables customers to quickly prepare and customize their virtual experiments, and only rely on ordinary desktop computers or mobile devices to simulate dozens of materials or devices. In short, it is to be able to get the results that can only be obtained by the previous lengthy experiments through computer simulation. On the one hand, it can reduce the test cost, on the other hand, it can save a lot of time.
According to the plan, the major cooperation between the two sides will focus on device simulation, which is what Bumblebee is good at. In the second step, the two sides plan to expand their cooperation to the research of luminescent materials, and carry out virtual simulation testing of luminescent materials, which can be analyzed, predicted and improved by computer. The second step is even an area that Simbeyond has never covered.
In fact, on the track of using organic light-emitting materials on OLEDs, it is not only Su Shijian and his team, but also other institutions around the world are carrying out similar research and development. Chinese enterprises have encountered more than once the “pain” of being charged with high patent fees. This is actually a wake-up call to the industry – whoever ignores basic innovation will be eliminated before the new era of display technology is fully arrived.
OLED’s next application scenario: car lighting
Compared with LCD, OLED has shown significant advantages in realizing large-area high-quality display and lighting, ultra-high resolution, ultra-fast response speed and flexible electronic applications. OLED is the control of electrons, and the reaction speed is fast. LCD needs backlight, so there is often light leakage, it is difficult to present pure black, and the reaction speed is also slow. The biggest competitor of OLED technology is laser display. Laser display technology has many advantages, such as wide range of color gamut, long life, high efficiency, low power consumption, energy conservation, environmental protection, lightweight, etc., so it has also attracted much attention.
Although the price is still relatively “local”, OLED has been applied in mobile phones, televisions and wearable devices. These are obviously not enough. So, what is the next application scenario of OLED? Su Shijian believes that lighting can be used not only for home lighting, but also for car lighting, especially for car tail lights.
OLED surface is based on the flexibility of the screen, which is “congenital”, so it has advantages in thickness, weight, visual angle, brightness, contrast, etc. Take the 55-inch OLED TV as an example, its thickness is only 7.5mm, which is equivalent to the thickness of an iPhone, and its weight is also relatively light, 10 kg, which is about 50% of the normal LCD TV.
In terms of the use effect, take the automobile tail lamp as an example, the automobile tail lamp mainly displays red light and yellow light, which requires high recognition, strong penetration, bright color and plump, which is also where OLED is superior to traditional halogen bulbs. At present, China’s automobile industry, which has taken the lead in the transformation to intelligent and electric, leads the world, and technology has become one of the largest labels of China’s automobile. The addition of OLED will undoubtedly enable China’s automobile innovation.
According to the latest comprehensive sales statistics of the Automobile Market Research Branch of the China Automobile Circulation Association (PCA), in October this year, the sales volume of the domestic narrow passenger car market reached 1.843 million, and the cumulative sales volume from January to October reached 16.626 million. This is just the sales of new cars, not counting the huge aftermarket. Chinese auto companies have always been “bold and dare to try”. They will dare to try OLED tail lights just as they dared to try LED headlights and vehicle-mounted interconnection.
There is no shortcut for basic innovation and technological research and development, but we can only persevere. What is the future technology route? We can argue, but we need to have our own firm views and attitudes. As a technologist and team, in the final analysis, we need to win the market with our capabilities and products. In recent years, China’s OLED field has made great achievements. Some people think it is lucky and the direction is wrong. But the fact is that behind the success of OLED in China, there are solid research and development achievements.