Who will win the future of display technologies?

Who will win the future of display technologies? Abstract In recent years, China and other countries have invested heavily in the research and manufacturing capacity of display technology. Meanwhile, different display technology scenarios, ranging from traditional LCD (liquid crystal display) to rapidly expanding OLED (organic light-emitting diode) and emerging QLED (quantum-dot light-emitting diode), are competing for market dominance. Amidst the trivium strife, OLED, backed by technology leader Apple's decision to use OLED for its iPhone X, seems to have a better position, yet QLED, despite still having technological obstacles to overcome, has displayed potential advantage in color quality, lower production costs and longer life. Which technology will win the heated competition? How have Chinese manufacturers and research institutes been prepared for display technology development? What policies should be enacted to encourage China's innovation and promote its international competitiveness? At an online forum organized by National Science Review, its associate editor-in-chief, Dongyuan Zhao, asked four leading experts and scientists in China.   Xiuqi Huang President of Research Institute at Visionox, a major OLED manufacturer    Liangsheng Liao Semiconductor physicist of Soochow University in Suzhou    Xiaogang Peng Chemist of Zhejiang University in Hangzhou    Jun Xu Material physicist of Fudan University in Shanghai    Dongyuan Zhao (Chair) Material chemist of Fudan University in Shanghai    Xiuqi Huang President of Research Institute at Visionox, a major OLED manufacturer    Liangsheng Liao Semiconductor physicist of Soochow University in Suzhou    Xiaogang Peng Chemist of Zhejiang University in Hangzhou    Jun Xu Material physicist of Fudan University in Shanghai    Dongyuan Zhao (Chair) Material chemist of Fudan University in Shanghai    Xiuqi Huang President of Research Institute at Visionox, a major OLED manufacturer    Liangsheng Liao Semiconductor physicist of Soochow University in Suzhou    Xiaogang Peng Chemist of Zhejiang University in Hangzhou    Jun Xu Material physicist of Fudan University in Shanghai    Dongyuan Zhao (Chair) Material chemist of Fudan University in Shanghai    Xiuqi Huang President of Research Institute at Visionox, a major OLED manufacturer    Liangsheng Liao Semiconductor physicist of Soochow University in Suzhou    Xiaogang Peng Chemist of Zhejiang University in Hangzhou    Jun Xu Material physicist of Fudan University in Shanghai    Dongyuan Zhao (Chair) Material chemist of Fudan University in Shanghai  RISING OLED CHALLENGES LCD Zhao: We all know display technologies are very important. Currently, there are OLED, QLED and traditional LCD technologies competing with each other. What are their differences and specific advantages? Shall we start from OLED? Huang: OLED has developed very quickly in recent years. It is better to compare it with traditional LCD if we want to have a clear understanding of its characteristics. In terms of structure, LCD largely consists of three parts: backlight, TFT backplane and cell, or liquid section for display. Different from LCD, OLED lights directly with electricity. Thus, it does not need backlight, but it still needs the TFT backplane to control where to light. Because it is free from backlight, OLED has a thinner body, higher response time, higher color contrast and lower power consumption. Potentially, it may even have a cost advantage over LCD. The biggest breakthrough is its flexible display, which seems very hard to achieve for LCD. Liao: Actually, there were/are many different types of display technologies, such as CRT (cathode ray tube), PDP (plasma display panel), LCD, LCOS (liquid crystals on silicon), laser display, LED (light-emitting diodes), SED (surface-conduction electron-emitter display), FED (filed emission display), OLED, QLED and Micro LED. From display technology lifespan point of view, Micro LED and QLED may be considered as in the introduction phase, OLED is in the growth phase, LCD for both computer and TV is in the maturity phase, but LCD for cellphone is in the decline phase, PDP and CRT are in the elimination phase. Now, LCD products are still dominating the display market while OLED is penetrating the market. As just mentioned by Dr Huang, OLED indeed has some advantages over LCD. Huang: Despite the apparent technological advantages of OLED over LCD, it is not straightforward for OLED to replace LCD. For example, although both OLED and LCD use the TFT backplane, the OLED’s TFT is much more difficult to be made than that of the voltage-driven LCD because OLED is current-driven. Generally speaking, problems for mass production of display technology can be divided into three categories, namely scientific problems, engineering problems and production problems. The ways and cycles to solve these three kinds of problems are different. At present, LCD has been relatively mature, while OLED is still in the early stage of industrial explosion. For OLED, there are still many urgent problems to be solved, especially production problems that need to be solved step by step in the process of mass production line. In addition, the capital threshold for both LCD and OLED are very high. Compared with the early development of LCD many years ago, the advancing pace of OLED has been quicker. While in the short term, OLED can hardly compete with LCD in large size screen, how about that people may change their use habit to give up large screen? —Jun Xu Liao: I want to supplement some data. According to the consulting firm HIS Markit, in 2018, the global market value for OLED products will be US$38.5 billion. But in 2020, it will reach US$67 billion, with an average compound annual growth rate of 46%. Another prediction estimates that OLED accounts for 33% of the display market sales, with the remaining 67% by LCD in 2018. But OLED’s market share could reach to 54% in 2020. Huang: While different sources may have different prediction, the advantage of OLED over LCD in small and medium-sized display screen is clear. In small-sized screen, such as smart watch and smart phone, the penetration rate of OLED is roughly 20% to 30%, which represents certain competitiveness. For large size screen, such as TV, the advancement of OLED [against LCD] may need more time. LCD FIGHTS BACK Xu: LCD was first proposed in 1968. During its development process, the technology has gradually overcome its own shortcomings and defeated other technologies. What are its remaining flaws? It is widely recognized that LCD is very hard to be made flexible. In addition, LCD does not emit light, so a back light is needed. The trend for display technologies is of course towards lighter and thinner (screen). But currently, LCD is very mature and economic. It far surpasses OLED, and its picture quality and display contrast do not lag behind. Currently, LCD technology's main target is head-mounted display (HMD), which means we must work on display resolution. In addition, OLED currently is only appropriate for medium and small-sized screens, but large screen has to rely on LCD. This is why the industry remains investing in the 10.5th generation production line (of LCD). Zhao: Do you think LCD will be replaced by OLED or QLED? Xu: While deeply impacted by OLED’s super thin and flexible display, we also need to analyse the insufficiency of OLED. With lighting material being organic, its display life might be shorter. LCD can easily be used for 100 000 hours. The other defense effort by LCD is to develop flexible screen to counterattack the flexible display of OLED. But it is true that big worries exist in LCD industry. LCD industry can also try other (counterattacking) strategies. We are advantageous in large-sized screen, but how about six or seven years later? While in the short term, OLED can hardly compete with LCD in large size screen, how about that people may change their use habit to give up large screen? People may not watch TV and only takes portable screens. Some experts working at a market survey institute CCID (China Center for Information Industry Development) predicted that in five to six years, OLED will be very influential in small and medium-sized screen. Similarly, a top executive of BOE Technology said that after five to six years, OLED will counterweigh or even surpass LCD in smaller sizes, but to catch up with LCD, it may need 10 to 15 years. MICRO LED EMERGES AS ANOTHER RIVALING TECHNOLOGY Xu: Besides LCD, Micro LED (Micro Light-Emitting Diode Display) has evolved for many years, though people's real attention to the display option was not aroused until May 2014 when Apple acquired US-based Micro LED developer LuxVue Technology. It is expected that Micro LED will be used on wearable digital devices to improve battery's life and screen brightness. Micro LED, also called mLED or μLED, is a new display technology. Using a so-called mass transfer technology, Micro LED displays consist of arrays of microscopic LEDs forming the individual pixel elements. It can offer better contrast, response times, very high resolution and energy efficiency. Compared with OLED, it has higher lightening efficiency and longer life span, but its flexible display is inferior to OLED. Compared with LCD, Micro LED has better contrast, response times and energy efficiency. It is widely considered appropriate for wearables, AR/VR, auto display and mini-projector. However, Micro LED still has some technological bottlenecks in epitaxy, mass transfer, driving circuit, full colorization, and monitoring and repairing. It also has a very high manufacturing cost. In short term, it cannot compete traditional LCD. But as a new generation of display technology after LCD and OLED, Micro LED has received wide attentions and it should enjoy fast commercialization in the coming three to five years. QUANTUM DOT JOINS THE COMPETITION Peng: It comes to quantum dot. First, QLED TV on market today is a misleading concept. Quantum dots are a class of semiconductor nanocrystals, whose emission wavelength can be continuously tuned because of the so-called quantum confinement effect. Because they are inorganic crystals, quantum dots in display devices are very stable. Also, due to their single crystalline nature, emission color of quantum dots can be extremely pure, which dictates the color quality of display devices. Interestingly, quantum dots as light-emitting materials are related to both OLED and LCD. The so-called QLED TVs on market are actually quantum-dot enhanced LCD TVs, which use quantum dots to replace the green and red phosphors in LCD’s backlight unit. By doing so, LCD displays greatly improve their color purity, picture quality and potentially energy consumption. The working mechanisms of quantum dots in these enhanced LCD displays is their photoluminescence. For its relationship with OLED, quantum-dot light-emitting diode (QLED) can in certain sense be considered as electroluminescence devices by replacing the organic light-emitting materials in OLED. Though QLED and OLED have nearly identical structure, they also have noticeable differences. Similar to LCD with quantum-dot backlighting unit, color gamut of QLED is much wider than that of OLED and it is more stable than OLED. Another big difference between OLED and QLED is their production technology. OLED relies on a high-precision technique called vacuum evaporation with high-resolution mask. QLED cannot be produced in this way because quantum dots as inorganic nanocrystals are very difficult to be vaporized. If QLED is commercially produced, it has to be printed and processed with solution-based technology. You can consider this as a weakness, since the printing electronics at present is far less precision than the vacuum-based technology. However, solution-based processing can also be considered as an advantage, because if the production problem is overcome, it costs much less than the vacuum-based technology applied for OLED. Without considering TFT, investment into an OLED production line often costs tens of billions of yuan but investment for QLED could be just 90–95% less. Given the relatively low resolution of printing technology, QLED shall be difficult to reach a resolution greater than 300 PPI (pixels per inch) within a few years. Thus, QLED might not be applied for small-sized displays at present and its potential will be medium to large-sized displays. Zhao: Quantum dots are inorganic nanocrystal, which means that they must be passivated with organic ligands for stability and function. How to solve this problem? Second, can commercial production of quantum dots reach an industrial scale? Peng: Good questions. Ligand chemistry of quantum dots has developed quickly in the past two to three years. Colloidal stability of inorganic nanocrystals should be said of being solved. We reported in 2016 that one gram of quantum dots can be stably dispersed in one milliliter of organic solution, which is certainly sufficient for printing technology. For the second question, several companies have been able to mass produce quantum dots. At present, all these production volume is built for fabrication of the backlighting units for LCD. It is believed that all high-end TVs from Samsung in 2017 are all LCD TVs with quantum-dot backlighting units. In addition, Nanosys in the United States is also producing quantum dots for LCD TVs. NajingTech at Hangzhou, China demonstrate production capacity to support the Chinese TV makers. To my knowledge, NajingTech is establishing a production line for 10 million sets of color TVs with quantum-dot backlighting units annually. China's current demands cannot be fully satisfied from the foreign companies. It is also necessary to fulfill the demands of domestic market. That is why China must develop its OLED production capability. —Liangsheng Liao CHINA’S RIVALS IN THE DISPLAY MARKET Zhao: South Korean companies have invested huge resources in OLED. Why? What can China learn from their experience? Huang: Based on my understanding of Samsung, the leading Korean player in OLED market, we cannot say it had foresight in the very beginning. Samsung began to invest in AMOLED (active-matrix organic light-emitting diode, a major type of OLED used in the display industry) in about 2003, and did not realize mass production until 2007. Its OLED production reached profitability in 2010. Since then, Samsung gradually secured a market monopoly status. So, originally, OLED was only one of Samsung's several alternative technology pathways. But step by step, it achieved an advantageous status in the market and so tended to maintain it by expanding its production capacity. Another reason is customers’ demands. Apple has refrained itself from using OLED for some years due to various reasons, including the patent disputes with Samsung. But after Apple began to use OLED for its iPhone X, it exerted a big influence in the whole industry. So now Samsung began to harvest its accumulated investments in the field and began to expand the capacity more. Also, Samsung has spent considerable time and efforts on the development of the product chain. Twenty or thirty years ago, Japan owned the most complete product chain for display products. But since Samsung entered the field in that time, it has spent huge energies to cultivate upstream and downstream Korean firms. Now the Republic of Korea (ROK) manufacturers began to occupy a large share in the market. Liao: South Korean manufacturers including Samsung and LG Electronics have controlled 90% of global supplies of medium and small-sized OLED panels. Since Apple began to buy OLED panels from Samsung for its cellphone products, there were no more enough panels shipping to China. Therefore, China's current demands cannot be fully satisfied from the foreign companies. On the other hand, because China has a huge market for cellphones, it would be necessary to fulfill the demands through domestic efforts. That is why China must develop its OLED production capability. Huang: The importance of China's LCD manufacturing is now globally high. Compared with the early stage of LCD development, China's status in OLED has been dramatically improved. When developing LCD, China has adopted the pattern of introduction-absorption-renovation. Now for OLED, we have a much higher percentage of independent innovation. Where are our advantages? First is the big market and our understanding of (domestic) customers’ demands. Then it is the scale of human resources. One big factory will create several thousand jobs, and it will mobilize a whole production chain, involving thousands of workers. The requirement of supplying these engineers and skilled workers can be fulfilled in China. The third advantage is the national supports. The government has input huge supports and manufacturers’ technological capacity is improving. I think Chinese manufacturers will have a great breakthrough in OLED. Although we cannot say that our advantages triumph over ROK, where Samsung and LG have been dominating the field for many years, we have achieved many significant progresses in developing the material and parts of OLED. We also have high level of innovation in process technology and designs. We already have several major manufacturers, such as Visionox, BOE, EDO and Tianma, which have owned significant technological reserves. CHANCES FOR CHINA TO DOMINATE QLED? Zhao: What is China's independent innovation or comparative technological advantages in QLED? Peng: As mentioned above, there are two ways to apply quantum dots for display, namely photoluminescence in backlighting For QLED, the three stages of technological development [from science issue to engineering and finally to mass production] have been mingled together at the same time. If one wants to win the competition, it is necessary to invest on all three dimensions. —Xiaogang Peng units for LCD and electroluminescence in QLED. For the photoluminescence applications, the key is quantum-dot materials. China has noticeable advantages in quantum-dot materials. After I returned to China, NajingTech (co-founded by Peng) purchased all key patents invented by me in the United States under the permission of US government. These patents cover the basic synthesis and processing technologies of quantum dots. NajingTech has already established capability for large-scale production of quantum dots. Comparatively, Korea—represented by Samsung—is the current leading company in all aspects of display industry, which offers great advantages in commercialization of quantum-dot displays. In late 2016, Samsung acquired QD Vision (a leading quantum-dot technology developer based in the United States). In addition, Samsung has invested heavily in purchasing quantum-dot-related patents and in developing the technology. China is internationally leading in electroluminescence at present. In fact, it was the 2014 Nature publication by a group of scientists from Zhejiang University that proved QLED can reach the stringent requirements for display applications. However, who will become the final winner of the international competition on electroluminescence remains unclear. China's investment in quantum-dot technology lags far behind US and ROK. Basically, the quantum-dot research has been centered in US for most of its history, and South Korean players have invested heavily along this direction as well. For electroluminescence, it is very likely to co-exist with OLED for a long period of time. This is so because, in small screen, QLED’s resolution is limited by printing technology. Zhao: Do you think QLED will have advantages over OLED in price or mass production? Will it be cheaper than LCD? Peng: If electroluminescence can be successfully achieved with printing, it will be much cheaper, with only about 1/10th cost of OLED. Manufacturers like NajingTech and BOE in China have demonstrated printing displays with quantum dots. At present, QLED does not compete with OLED directly, given its market in small-sized screen. A while ago, Dr. Huang mentioned three stages of technological development, from science issue to engineering and finally to mass production. For QLED, the three stages have been mingled together at the same time. If one wants to win the competition, it is necessary to invest on all three dimensions. Huang: When OLED was compared with LCD in the past, lots of advantages of OLED were highlighted, such as high color gamut, high contrast and high response speed and so on. But above advantages would be difficult to be the overwhelming superiority to make the consumers to choose replacement. It seems to be possible that the flexible display will eventually lead a killer advantage. I think QLED will also face similar situation. What is its real advantage if it is compared with OLED or LCD? For QLED, it seems to have been difficult to find the advantage in small screen. Dr. Peng has suggested its advantage lies in medium-sized screen, but what is its uniqueness? Peng: The two types of key advantages of QLED are discussed above. One, QLED is based on solution-based printing technology, which is low cost and high yield. Two, quantum-dot emitters vender QLED with a large color gamut, high picture quality and superior device lifetime. Medium-sized screen is easiest for the coming QLED technologies but QLED for large screen is probably a reasonable extension afterwards. Huang: But customers may not accept only better wider color range if they need to pay more money for this. I would suggest QLED consider the changes in color standards, such as the newly released BT2020 (defining high-definition 4 K TV), and new unique applications which cannot be satisfied by other technologies. The future of QLED seems also relying on the maturity of printing technology. Peng: New standard (BT2020) certainly helps QLED, given BT2020 meaning a broad color gamut. Among the technologies discussed today, quantum-dot displays in either form are the only ones that can satisfy BT2020 without any optical compensation. In addition, studies found that the picture quality of display is highly associated with color gamut. It is correct that the maturity of printing technology plays an important role in the development of QLED. The current printing technology is ready for medium-sized screen and should be able to be extended to large-sized screen without much trouble. REFORMING RESEARCH AND TRAINING SYSTEMS TO PROMOTE DISPLAY TECHNOLOGY Xu: For QLED to become a dominant technology, it is still difficult. In its development process, OLED precedes it and there are other rivaling technologies following. While we know owning the foundational patents and core technologies of QLED can make you a good position, holding core technologies alone cannot ensure you to become a mainstream technology. The government's investment in such key technologies after all is small as compared with industry and cannot decide QLED to become mainstream technology. Peng: Domestic industry sector has begun to invest in these future technologies. For example, NajingTech has invested about 400 million yuan ($65 million) in QLED, primarily in electroluminescence. There are some leading domestic players having invested into the field. Yes, this is far from enough. For example, there are few domestic companies investing R&D of printing technologies. Our printing equipment is primarily made by the US, European and Japan players. I think this is also a chance for China (to develop the printing technologies). Xu: Our industry wants to collaborate with universities and research institutes to develop kernel innovative technologies. Currently they heavily rely on imported equipment. A stronger industry-academics collaboration should help solve some of the problems. Liao: Due to their lack of kernel technologies, Chinese OLED panel manufacturers heavily rely on investments to improve their market competitiveness. But this may cause the overheated investment in the OLED industry. In recent years, China has already imported quite a few new OLED production lines with the total cost of about 450 billion yuan (US$71.5 billion). Lots of advantages of OLED over LCD were highlighted, such as high color gamut, high contrast and high response speed and so on …. It seems to be possible that the flexible display will eventually lead a killer advantage. —Xiuqi Huang The short of talent human resources perhaps is another issue to influence the fast expansion of the industry domestically. For an example, BOE alone demands more than 1000 new engineers last year. However, the domestic universities certainly cannot fulfill this requirement for specially trained OLED working forces currently. A major problem is the training is not implemented in accordance with industry demands but surrounding academic papers. Huang: The talent training in ROK is very different. In Korea, many doctoral students are doing almost the same thing in universities or research institutes as they do in large enterprises, which is very helpful for them to get started quickly after entering the company. On the other hand, many professors of universities or research institutes have working experience of large enterprises, which makes universities better understand the demand of industry. Liao: However, Chinese researchers’ priority pursuit of papers is in disjunction from industry demand. Majority of people (at universities) who are working on organic optoelectronics are more interested in the fields of QLED, organic solar cells, perovskite solar cells and thin-film transistors because they are trendy fields and have more chances to publish research papers. On the other hand, many studies that are essential to solve industry's problems, such as developing domestic versions of equipment, are not so essential for paper publication, so that faculty and students shed from them. Xu: It is understandable. Students do not want to work on the applications too much because they need to publish papers to graduate. Universities also demand short-term research outcomes. A possible solution is to set up an industry-academics sharing platform for professionals and resources from the two sides to move to each other. Academics should develop truly original basic research. Industry wants to collaborate with professors owning such original innovative research. Zhao: Today there are really good observations, discussions and suggestions. The industry-academics-research collaboration is crucial to the future of China's display technologies. We all should work hard on this. © The Author(s) 2018. Published by Oxford University Press on behalf of China Science Publishing & Media Ltd. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/about_us/legal/notices) http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png National Science Review Oxford University Press

Who will win the future of display technologies?

National Science Review , Volume Advance Article (3) – Apr 23, 2018

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Oxford University Press
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© The Author(s) 2018. Published by Oxford University Press on behalf of China Science Publishing & Media Ltd.
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2095-5138
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Abstract

Abstract In recent years, China and other countries have invested heavily in the research and manufacturing capacity of display technology. Meanwhile, different display technology scenarios, ranging from traditional LCD (liquid crystal display) to rapidly expanding OLED (organic light-emitting diode) and emerging QLED (quantum-dot light-emitting diode), are competing for market dominance. Amidst the trivium strife, OLED, backed by technology leader Apple's decision to use OLED for its iPhone X, seems to have a better position, yet QLED, despite still having technological obstacles to overcome, has displayed potential advantage in color quality, lower production costs and longer life. Which technology will win the heated competition? How have Chinese manufacturers and research institutes been prepared for display technology development? What policies should be enacted to encourage China's innovation and promote its international competitiveness? At an online forum organized by National Science Review, its associate editor-in-chief, Dongyuan Zhao, asked four leading experts and scientists in China.   Xiuqi Huang President of Research Institute at Visionox, a major OLED manufacturer    Liangsheng Liao Semiconductor physicist of Soochow University in Suzhou    Xiaogang Peng Chemist of Zhejiang University in Hangzhou    Jun Xu Material physicist of Fudan University in Shanghai    Dongyuan Zhao (Chair) Material chemist of Fudan University in Shanghai    Xiuqi Huang President of Research Institute at Visionox, a major OLED manufacturer    Liangsheng Liao Semiconductor physicist of Soochow University in Suzhou    Xiaogang Peng Chemist of Zhejiang University in Hangzhou    Jun Xu Material physicist of Fudan University in Shanghai    Dongyuan Zhao (Chair) Material chemist of Fudan University in Shanghai    Xiuqi Huang President of Research Institute at Visionox, a major OLED manufacturer    Liangsheng Liao Semiconductor physicist of Soochow University in Suzhou    Xiaogang Peng Chemist of Zhejiang University in Hangzhou    Jun Xu Material physicist of Fudan University in Shanghai    Dongyuan Zhao (Chair) Material chemist of Fudan University in Shanghai    Xiuqi Huang President of Research Institute at Visionox, a major OLED manufacturer    Liangsheng Liao Semiconductor physicist of Soochow University in Suzhou    Xiaogang Peng Chemist of Zhejiang University in Hangzhou    Jun Xu Material physicist of Fudan University in Shanghai    Dongyuan Zhao (Chair) Material chemist of Fudan University in Shanghai  RISING OLED CHALLENGES LCD Zhao: We all know display technologies are very important. Currently, there are OLED, QLED and traditional LCD technologies competing with each other. What are their differences and specific advantages? Shall we start from OLED? Huang: OLED has developed very quickly in recent years. It is better to compare it with traditional LCD if we want to have a clear understanding of its characteristics. In terms of structure, LCD largely consists of three parts: backlight, TFT backplane and cell, or liquid section for display. Different from LCD, OLED lights directly with electricity. Thus, it does not need backlight, but it still needs the TFT backplane to control where to light. Because it is free from backlight, OLED has a thinner body, higher response time, higher color contrast and lower power consumption. Potentially, it may even have a cost advantage over LCD. The biggest breakthrough is its flexible display, which seems very hard to achieve for LCD. Liao: Actually, there were/are many different types of display technologies, such as CRT (cathode ray tube), PDP (plasma display panel), LCD, LCOS (liquid crystals on silicon), laser display, LED (light-emitting diodes), SED (surface-conduction electron-emitter display), FED (filed emission display), OLED, QLED and Micro LED. From display technology lifespan point of view, Micro LED and QLED may be considered as in the introduction phase, OLED is in the growth phase, LCD for both computer and TV is in the maturity phase, but LCD for cellphone is in the decline phase, PDP and CRT are in the elimination phase. Now, LCD products are still dominating the display market while OLED is penetrating the market. As just mentioned by Dr Huang, OLED indeed has some advantages over LCD. Huang: Despite the apparent technological advantages of OLED over LCD, it is not straightforward for OLED to replace LCD. For example, although both OLED and LCD use the TFT backplane, the OLED’s TFT is much more difficult to be made than that of the voltage-driven LCD because OLED is current-driven. Generally speaking, problems for mass production of display technology can be divided into three categories, namely scientific problems, engineering problems and production problems. The ways and cycles to solve these three kinds of problems are different. At present, LCD has been relatively mature, while OLED is still in the early stage of industrial explosion. For OLED, there are still many urgent problems to be solved, especially production problems that need to be solved step by step in the process of mass production line. In addition, the capital threshold for both LCD and OLED are very high. Compared with the early development of LCD many years ago, the advancing pace of OLED has been quicker. While in the short term, OLED can hardly compete with LCD in large size screen, how about that people may change their use habit to give up large screen? —Jun Xu Liao: I want to supplement some data. According to the consulting firm HIS Markit, in 2018, the global market value for OLED products will be US$38.5 billion. But in 2020, it will reach US$67 billion, with an average compound annual growth rate of 46%. Another prediction estimates that OLED accounts for 33% of the display market sales, with the remaining 67% by LCD in 2018. But OLED’s market share could reach to 54% in 2020. Huang: While different sources may have different prediction, the advantage of OLED over LCD in small and medium-sized display screen is clear. In small-sized screen, such as smart watch and smart phone, the penetration rate of OLED is roughly 20% to 30%, which represents certain competitiveness. For large size screen, such as TV, the advancement of OLED [against LCD] may need more time. LCD FIGHTS BACK Xu: LCD was first proposed in 1968. During its development process, the technology has gradually overcome its own shortcomings and defeated other technologies. What are its remaining flaws? It is widely recognized that LCD is very hard to be made flexible. In addition, LCD does not emit light, so a back light is needed. The trend for display technologies is of course towards lighter and thinner (screen). But currently, LCD is very mature and economic. It far surpasses OLED, and its picture quality and display contrast do not lag behind. Currently, LCD technology's main target is head-mounted display (HMD), which means we must work on display resolution. In addition, OLED currently is only appropriate for medium and small-sized screens, but large screen has to rely on LCD. This is why the industry remains investing in the 10.5th generation production line (of LCD). Zhao: Do you think LCD will be replaced by OLED or QLED? Xu: While deeply impacted by OLED’s super thin and flexible display, we also need to analyse the insufficiency of OLED. With lighting material being organic, its display life might be shorter. LCD can easily be used for 100 000 hours. The other defense effort by LCD is to develop flexible screen to counterattack the flexible display of OLED. But it is true that big worries exist in LCD industry. LCD industry can also try other (counterattacking) strategies. We are advantageous in large-sized screen, but how about six or seven years later? While in the short term, OLED can hardly compete with LCD in large size screen, how about that people may change their use habit to give up large screen? People may not watch TV and only takes portable screens. Some experts working at a market survey institute CCID (China Center for Information Industry Development) predicted that in five to six years, OLED will be very influential in small and medium-sized screen. Similarly, a top executive of BOE Technology said that after five to six years, OLED will counterweigh or even surpass LCD in smaller sizes, but to catch up with LCD, it may need 10 to 15 years. MICRO LED EMERGES AS ANOTHER RIVALING TECHNOLOGY Xu: Besides LCD, Micro LED (Micro Light-Emitting Diode Display) has evolved for many years, though people's real attention to the display option was not aroused until May 2014 when Apple acquired US-based Micro LED developer LuxVue Technology. It is expected that Micro LED will be used on wearable digital devices to improve battery's life and screen brightness. Micro LED, also called mLED or μLED, is a new display technology. Using a so-called mass transfer technology, Micro LED displays consist of arrays of microscopic LEDs forming the individual pixel elements. It can offer better contrast, response times, very high resolution and energy efficiency. Compared with OLED, it has higher lightening efficiency and longer life span, but its flexible display is inferior to OLED. Compared with LCD, Micro LED has better contrast, response times and energy efficiency. It is widely considered appropriate for wearables, AR/VR, auto display and mini-projector. However, Micro LED still has some technological bottlenecks in epitaxy, mass transfer, driving circuit, full colorization, and monitoring and repairing. It also has a very high manufacturing cost. In short term, it cannot compete traditional LCD. But as a new generation of display technology after LCD and OLED, Micro LED has received wide attentions and it should enjoy fast commercialization in the coming three to five years. QUANTUM DOT JOINS THE COMPETITION Peng: It comes to quantum dot. First, QLED TV on market today is a misleading concept. Quantum dots are a class of semiconductor nanocrystals, whose emission wavelength can be continuously tuned because of the so-called quantum confinement effect. Because they are inorganic crystals, quantum dots in display devices are very stable. Also, due to their single crystalline nature, emission color of quantum dots can be extremely pure, which dictates the color quality of display devices. Interestingly, quantum dots as light-emitting materials are related to both OLED and LCD. The so-called QLED TVs on market are actually quantum-dot enhanced LCD TVs, which use quantum dots to replace the green and red phosphors in LCD’s backlight unit. By doing so, LCD displays greatly improve their color purity, picture quality and potentially energy consumption. The working mechanisms of quantum dots in these enhanced LCD displays is their photoluminescence. For its relationship with OLED, quantum-dot light-emitting diode (QLED) can in certain sense be considered as electroluminescence devices by replacing the organic light-emitting materials in OLED. Though QLED and OLED have nearly identical structure, they also have noticeable differences. Similar to LCD with quantum-dot backlighting unit, color gamut of QLED is much wider than that of OLED and it is more stable than OLED. Another big difference between OLED and QLED is their production technology. OLED relies on a high-precision technique called vacuum evaporation with high-resolution mask. QLED cannot be produced in this way because quantum dots as inorganic nanocrystals are very difficult to be vaporized. If QLED is commercially produced, it has to be printed and processed with solution-based technology. You can consider this as a weakness, since the printing electronics at present is far less precision than the vacuum-based technology. However, solution-based processing can also be considered as an advantage, because if the production problem is overcome, it costs much less than the vacuum-based technology applied for OLED. Without considering TFT, investment into an OLED production line often costs tens of billions of yuan but investment for QLED could be just 90–95% less. Given the relatively low resolution of printing technology, QLED shall be difficult to reach a resolution greater than 300 PPI (pixels per inch) within a few years. Thus, QLED might not be applied for small-sized displays at present and its potential will be medium to large-sized displays. Zhao: Quantum dots are inorganic nanocrystal, which means that they must be passivated with organic ligands for stability and function. How to solve this problem? Second, can commercial production of quantum dots reach an industrial scale? Peng: Good questions. Ligand chemistry of quantum dots has developed quickly in the past two to three years. Colloidal stability of inorganic nanocrystals should be said of being solved. We reported in 2016 that one gram of quantum dots can be stably dispersed in one milliliter of organic solution, which is certainly sufficient for printing technology. For the second question, several companies have been able to mass produce quantum dots. At present, all these production volume is built for fabrication of the backlighting units for LCD. It is believed that all high-end TVs from Samsung in 2017 are all LCD TVs with quantum-dot backlighting units. In addition, Nanosys in the United States is also producing quantum dots for LCD TVs. NajingTech at Hangzhou, China demonstrate production capacity to support the Chinese TV makers. To my knowledge, NajingTech is establishing a production line for 10 million sets of color TVs with quantum-dot backlighting units annually. China's current demands cannot be fully satisfied from the foreign companies. It is also necessary to fulfill the demands of domestic market. That is why China must develop its OLED production capability. —Liangsheng Liao CHINA’S RIVALS IN THE DISPLAY MARKET Zhao: South Korean companies have invested huge resources in OLED. Why? What can China learn from their experience? Huang: Based on my understanding of Samsung, the leading Korean player in OLED market, we cannot say it had foresight in the very beginning. Samsung began to invest in AMOLED (active-matrix organic light-emitting diode, a major type of OLED used in the display industry) in about 2003, and did not realize mass production until 2007. Its OLED production reached profitability in 2010. Since then, Samsung gradually secured a market monopoly status. So, originally, OLED was only one of Samsung's several alternative technology pathways. But step by step, it achieved an advantageous status in the market and so tended to maintain it by expanding its production capacity. Another reason is customers’ demands. Apple has refrained itself from using OLED for some years due to various reasons, including the patent disputes with Samsung. But after Apple began to use OLED for its iPhone X, it exerted a big influence in the whole industry. So now Samsung began to harvest its accumulated investments in the field and began to expand the capacity more. Also, Samsung has spent considerable time and efforts on the development of the product chain. Twenty or thirty years ago, Japan owned the most complete product chain for display products. But since Samsung entered the field in that time, it has spent huge energies to cultivate upstream and downstream Korean firms. Now the Republic of Korea (ROK) manufacturers began to occupy a large share in the market. Liao: South Korean manufacturers including Samsung and LG Electronics have controlled 90% of global supplies of medium and small-sized OLED panels. Since Apple began to buy OLED panels from Samsung for its cellphone products, there were no more enough panels shipping to China. Therefore, China's current demands cannot be fully satisfied from the foreign companies. On the other hand, because China has a huge market for cellphones, it would be necessary to fulfill the demands through domestic efforts. That is why China must develop its OLED production capability. Huang: The importance of China's LCD manufacturing is now globally high. Compared with the early stage of LCD development, China's status in OLED has been dramatically improved. When developing LCD, China has adopted the pattern of introduction-absorption-renovation. Now for OLED, we have a much higher percentage of independent innovation. Where are our advantages? First is the big market and our understanding of (domestic) customers’ demands. Then it is the scale of human resources. One big factory will create several thousand jobs, and it will mobilize a whole production chain, involving thousands of workers. The requirement of supplying these engineers and skilled workers can be fulfilled in China. The third advantage is the national supports. The government has input huge supports and manufacturers’ technological capacity is improving. I think Chinese manufacturers will have a great breakthrough in OLED. Although we cannot say that our advantages triumph over ROK, where Samsung and LG have been dominating the field for many years, we have achieved many significant progresses in developing the material and parts of OLED. We also have high level of innovation in process technology and designs. We already have several major manufacturers, such as Visionox, BOE, EDO and Tianma, which have owned significant technological reserves. CHANCES FOR CHINA TO DOMINATE QLED? Zhao: What is China's independent innovation or comparative technological advantages in QLED? Peng: As mentioned above, there are two ways to apply quantum dots for display, namely photoluminescence in backlighting For QLED, the three stages of technological development [from science issue to engineering and finally to mass production] have been mingled together at the same time. If one wants to win the competition, it is necessary to invest on all three dimensions. —Xiaogang Peng units for LCD and electroluminescence in QLED. For the photoluminescence applications, the key is quantum-dot materials. China has noticeable advantages in quantum-dot materials. After I returned to China, NajingTech (co-founded by Peng) purchased all key patents invented by me in the United States under the permission of US government. These patents cover the basic synthesis and processing technologies of quantum dots. NajingTech has already established capability for large-scale production of quantum dots. Comparatively, Korea—represented by Samsung—is the current leading company in all aspects of display industry, which offers great advantages in commercialization of quantum-dot displays. In late 2016, Samsung acquired QD Vision (a leading quantum-dot technology developer based in the United States). In addition, Samsung has invested heavily in purchasing quantum-dot-related patents and in developing the technology. China is internationally leading in electroluminescence at present. In fact, it was the 2014 Nature publication by a group of scientists from Zhejiang University that proved QLED can reach the stringent requirements for display applications. However, who will become the final winner of the international competition on electroluminescence remains unclear. China's investment in quantum-dot technology lags far behind US and ROK. Basically, the quantum-dot research has been centered in US for most of its history, and South Korean players have invested heavily along this direction as well. For electroluminescence, it is very likely to co-exist with OLED for a long period of time. This is so because, in small screen, QLED’s resolution is limited by printing technology. Zhao: Do you think QLED will have advantages over OLED in price or mass production? Will it be cheaper than LCD? Peng: If electroluminescence can be successfully achieved with printing, it will be much cheaper, with only about 1/10th cost of OLED. Manufacturers like NajingTech and BOE in China have demonstrated printing displays with quantum dots. At present, QLED does not compete with OLED directly, given its market in small-sized screen. A while ago, Dr. Huang mentioned three stages of technological development, from science issue to engineering and finally to mass production. For QLED, the three stages have been mingled together at the same time. If one wants to win the competition, it is necessary to invest on all three dimensions. Huang: When OLED was compared with LCD in the past, lots of advantages of OLED were highlighted, such as high color gamut, high contrast and high response speed and so on. But above advantages would be difficult to be the overwhelming superiority to make the consumers to choose replacement. It seems to be possible that the flexible display will eventually lead a killer advantage. I think QLED will also face similar situation. What is its real advantage if it is compared with OLED or LCD? For QLED, it seems to have been difficult to find the advantage in small screen. Dr. Peng has suggested its advantage lies in medium-sized screen, but what is its uniqueness? Peng: The two types of key advantages of QLED are discussed above. One, QLED is based on solution-based printing technology, which is low cost and high yield. Two, quantum-dot emitters vender QLED with a large color gamut, high picture quality and superior device lifetime. Medium-sized screen is easiest for the coming QLED technologies but QLED for large screen is probably a reasonable extension afterwards. Huang: But customers may not accept only better wider color range if they need to pay more money for this. I would suggest QLED consider the changes in color standards, such as the newly released BT2020 (defining high-definition 4 K TV), and new unique applications which cannot be satisfied by other technologies. The future of QLED seems also relying on the maturity of printing technology. Peng: New standard (BT2020) certainly helps QLED, given BT2020 meaning a broad color gamut. Among the technologies discussed today, quantum-dot displays in either form are the only ones that can satisfy BT2020 without any optical compensation. In addition, studies found that the picture quality of display is highly associated with color gamut. It is correct that the maturity of printing technology plays an important role in the development of QLED. The current printing technology is ready for medium-sized screen and should be able to be extended to large-sized screen without much trouble. REFORMING RESEARCH AND TRAINING SYSTEMS TO PROMOTE DISPLAY TECHNOLOGY Xu: For QLED to become a dominant technology, it is still difficult. In its development process, OLED precedes it and there are other rivaling technologies following. While we know owning the foundational patents and core technologies of QLED can make you a good position, holding core technologies alone cannot ensure you to become a mainstream technology. The government's investment in such key technologies after all is small as compared with industry and cannot decide QLED to become mainstream technology. Peng: Domestic industry sector has begun to invest in these future technologies. For example, NajingTech has invested about 400 million yuan ($65 million) in QLED, primarily in electroluminescence. There are some leading domestic players having invested into the field. Yes, this is far from enough. For example, there are few domestic companies investing R&D of printing technologies. Our printing equipment is primarily made by the US, European and Japan players. I think this is also a chance for China (to develop the printing technologies). Xu: Our industry wants to collaborate with universities and research institutes to develop kernel innovative technologies. Currently they heavily rely on imported equipment. A stronger industry-academics collaboration should help solve some of the problems. Liao: Due to their lack of kernel technologies, Chinese OLED panel manufacturers heavily rely on investments to improve their market competitiveness. But this may cause the overheated investment in the OLED industry. In recent years, China has already imported quite a few new OLED production lines with the total cost of about 450 billion yuan (US$71.5 billion). Lots of advantages of OLED over LCD were highlighted, such as high color gamut, high contrast and high response speed and so on …. It seems to be possible that the flexible display will eventually lead a killer advantage. —Xiuqi Huang The short of talent human resources perhaps is another issue to influence the fast expansion of the industry domestically. For an example, BOE alone demands more than 1000 new engineers last year. However, the domestic universities certainly cannot fulfill this requirement for specially trained OLED working forces currently. A major problem is the training is not implemented in accordance with industry demands but surrounding academic papers. Huang: The talent training in ROK is very different. In Korea, many doctoral students are doing almost the same thing in universities or research institutes as they do in large enterprises, which is very helpful for them to get started quickly after entering the company. On the other hand, many professors of universities or research institutes have working experience of large enterprises, which makes universities better understand the demand of industry. Liao: However, Chinese researchers’ priority pursuit of papers is in disjunction from industry demand. Majority of people (at universities) who are working on organic optoelectronics are more interested in the fields of QLED, organic solar cells, perovskite solar cells and thin-film transistors because they are trendy fields and have more chances to publish research papers. On the other hand, many studies that are essential to solve industry's problems, such as developing domestic versions of equipment, are not so essential for paper publication, so that faculty and students shed from them. Xu: It is understandable. Students do not want to work on the applications too much because they need to publish papers to graduate. Universities also demand short-term research outcomes. A possible solution is to set up an industry-academics sharing platform for professionals and resources from the two sides to move to each other. Academics should develop truly original basic research. Industry wants to collaborate with professors owning such original innovative research. Zhao: Today there are really good observations, discussions and suggestions. The industry-academics-research collaboration is crucial to the future of China's display technologies. We all should work hard on this. © The Author(s) 2018. Published by Oxford University Press on behalf of China Science Publishing & Media Ltd. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/about_us/legal/notices)

Journal

National Science ReviewOxford University Press

Published: Apr 23, 2018

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