月份：2012年9月

Factors that constrained the development of LED highway applications

LED technology has a lot of advantages. But in practical, applications of LED lighting sources still have many restrictions, which have been the largest obstacles in the path of LED highway applications.

 

Factors that constrained the development of LED highway applications

 

1)       Heat dissipation.

Improving the heat problem of LED lights is always one of the biggest challenges for LED manufactures. The working condition and heat dissipation is the two major factors that can determine the real light efficiency of LED lamps and certainly the service life of them. Generally, when we discussed about the light efficiency of LED lamps, we were talking about the light efficiency with an junction temperature of 25℃. However, due to cooling designs and influences from surrounding temperatures, it is usually higher than 25℃ in practices. That means, in real applications, the measured light efficiency will be less than the theoretical value. A theoretically 100lm/W LED chip used in LED highway applications may only have a real light efficiency of 60-70lm/W.

LHP is an advanced cooling technology for LED lighting products which has been recently invented by a technological company from Taiwan. This technique was first invented to replay traditional heat sink, which has well solved the problem mentioned above and dramatically increase the service life of LED chips. In order to prove the superiorities of LHP, thousands of LED chips were selected to take a 3-year special aging test (light attenuation test). During these tests, selected LEDs should take constant work for 12 hours per day. After 3 years, the measured light attenuation was less than 3%. It is estimated that after 10 years, the average light attenuation of these chips will be only 20%.

 

2)       Cost-effective problem.

Presently, prices of LED chips were still in a high level, causing LED street lights cost much more than traditional street lamps. However, there are also some people believe that prices of LED lighting applications will drop into a much more reasonable level, for the reason that LED is a kind of semiconductor components and the continuous development of micro-electrical industry. At present, the highest light efficiency of LED chips is around 150lm/W. And it is estimated that after ten years, the light efficiency of LEDs can reach up to 350lm/W. Thus it can be seen that LED highway applications actually has huge potentials.

How does LED lighting industry become bigger and stronger (one)

Today, under the background of  energy shortage, environmental degradation, “energy saving” has become the main task of the Governments, and China is no exception.

How does LED lighting industry become bigger and stronger (one)

LED lighting technology by virtue of its high performance, long life and other advantages in energy saving, everyone touted the “superstar”. all levels of government spared no expense to support it, in order to “energy saving” policy; brightest investment and private capital investment directed as its “huge market” have pocket it; various research institutions have been “merry” reorientation aimed at it; Various civil society organizations also can not wait to be included in the scope of business. Especially after the global financial crisis, with the introduction of the scheme of the huge new energy plan of the new Obama administration in the United States and the Chinese government to expand domestic demand in most other high-tech industries hit by the crisis, the LED lighting industry seems “the scenery here is fine.”

However, the LED industry in China, the new darling of the beautiful LED lights, we should think calmly about the fundamental issues that the fundamental issues that overshadowed prosperity surface.

First, what is the core issue of China’a LED lighting industry?

From the application point of view, the main market of the LED is lighting, display and backlight. Display application market has matured, the back light market is maturing. Greater than the impact of these two aspects of the market by the financial crisis. However, whenever from the government “energy saving” sense or potential size of the market from the point of view or from the direction of technology development visit lighting applications are deserved is the top priority of the LED market. This is why Europe and the United States national attention to the root causes of the LED technology. So, talk about LED in this passage, it also focus on the lighting market.

The core problem for LED lighting industry is not that the middle and lower reaches of the package and application, but in the upper reaches of the high-end chip. Imagine, if China has been the lack of high-end LED chip, even invested ten times funds in the demonstration project. That is only for foreign chip makers in China to earn more profits.

OLED applications used in display and lighting industry

The rapid development of OLED technology contributed to its continuous improvement of surface area, light efficiency and service life. OLED applications area started to transfer from small-sized portable terminal applications to large-sized computer/TV screens. Recently, they show the sign of penetration in the general lighting field. In addition, they also have huge potentials in the fields of military, aerospace and other applications.

 

OLED applications used in display and lighitng industry

 

Display area:

With Samsung having launched high-end mobiles with OLED main screen (5.3-inch and 4.3-inch AMOLED screen), the 6-inches AMOLED continued to increase the occupation of the market. After the promoting of 6-12 inches AMOLED screen, OLED may probably be used as high-end displays for tablet PCs. It is reported that, in the forthcoming exhibition CES-2012, Toshiba are planning to exhibit tablet PCs with 7-inch OLED screens produced by Samsung. Many giant manufacturers of display announced the plan of promoting large-sized OLED TVs, showing the confidence of occupying TV market. LG claimed that they will promote the world’s biggest OLED TV panels (55 inches) in the coming CES-2012.

 

General lighting industry:

OLED lighting applications have higher CRI and belong to surface-emitting, not only can present natural and soft rays but also provide more creative space for designers in appearance. So far, OLED is still underperformed than LED lights technology in various areas: light efficiency, service life and prices, etc. Many giant companies treated this as an opportunity and actively expand the market. From the second half of 2011, NEC, Konica Minolta, Toshiba, Panasonic and other large manufacturers revealed OLED applications in recent lighting exhibitions. It is expected that in 2012 Frankfurt Fair, OLED lighting products have become a new bright spot. OSRAM, Philips, LG, Novaled, Ronda, Sumitomo Chemical exhibited their products. The Japan government also expressed their willingness in developing the OLED industry. on 30th of March in 2012, OLED applications has been installed in Jiyugaoka Station (one of the stations that on Tokyo line). All these lamps were produced by Panasonic, with a light efficiency of 30lm/W, an 80mm x 80mm panel will costs 30,000 yen. KANEKA announced that they will start to promote their OLED products to restaurants since April in 2011 and promote OLED lighting applications to residences and offices since 2015.

Comparisons between high pressure sodium lighting and LED highway lighting

LED and high pressure sodium are two major lighting technologies that used in road lighting applications, including highway lighting. They are two different lighting sources. Lighting effects (luminous flux, service life, CRI, color temperature, light intensity, light efficiency) are various due to totally different lighting principles.

 

Comparisons between high pressure sodium lighting and LED highway lighting

 

High pressure sodium lamps have higher light efficiency, longer working life, stronger penetrability and free of bugs. Normally, the power consumption of high pressure sodium lamps can reach up to several KW, which can satisfy most lighting requirements. After being developing for several decade years, the lighting sources and technologies have already been full-fledged. Thus the production costs of these products dropped into a certain low level. For example, the average price of high pressure sodium tunnel lamps with high IP levels is only hundreds yuan. Although high pressure sodium lamps have been widely used in road lighting and tunnel lighting field, they still have some disadvantages that hard to be improved: 1) lower color temperature, normally send out yellow rays. And also lower CRI, only 20% of the natural light. 2) Although that high-powered high pressure sodium lights satisfied almost all demands from customers in illumination aspect, they still consumed too much energy. Traditional high pressure sodium lighting systems often loaded heavy burdens on operators’ shoulders. High pressure sodium lights have relatively short service life. According to its technology, the best lamps can only maintain a normal work for about 25,000 hours. In some rural areas, with very unstable power grids and severe weather conditions, the life of lighting sources of high pressure sodium lamps will be even shorter.

 

As the fourth generation of lighting sources, LED highway lighting applications have following advantages: 1) soft rays, high CRI (much closed to the sunlight compared with light generated by high pressure sodium lamps). 2) Fast respond in the switch on/off, almost no delay and these processes will cause ignorable damages to the lamps. 3) LEDs have longer service life; also some disadvantages: 1) Since LEDs are semiconductor lighting sources, they over-heated working conditions will reduce their theoretical working lives. Thus, cooling problem was always one of the biggest troubles for LED highway lighting application manufactures. 3) Poor penetration, when used in tunnels (in the high way), a good penetration of lamps will reduce the risk of accidents.

 

Both high pressure sodium lamps and LED highway lighting products have their advantages and disadvantages. Although LED lights are more sophisticated than high pressure sodium lamps in many ways, there still a lot of problems need to be solved.

Misunderstandings of highway LED lighting

How to look at the highway LED lighting? It is such a clear topic since there are so many practical applications that can be referred to both in theory and application area. As the matter of fact, highway LED lighting is humble in the application area, the “overheated” phenomenon in LED lighting industry exerted negative effects both on customers and manufacturers. However, failure cases are always followed with successful stories. The expensive material costs made the initial investments nearly unbearable. Under the government supports through energy conservation policies, highway LED applications entered a new era. Do these lamps have more use value than traditional high-way lamps and be more suitable for high-way conditions?

 

How to look at the highway LED lighting? It is such a clear topic since there are so many practical applications that can be referred to both in theory and application area.

 

As the new lighting technology, LED has many advantages: long service life, high light efficiency, low power consumption, good dimming performance, good CRI, anti-vibration, single-direction lighting sources, environmental friendly. In one word, LED technology has been seen with huge potentials in the lighting market. Many domestic LED application manufacturers have shifted their attention into highway LED lighting area as a result of the rapid development of high-powered LED lighting technology. However, the domestic lighting industry seems to move into a vicious circle “LED=green lighting”. They placed too much value on LED but ignore the importance of traditional lighting applications. Mr. Tao Zhang from Lighting Management of Lianyungang, Jiangsu Province indicated that not only LED that can be marked as green lighting technology. In fact, many exiting lighting technology can be classified as green lighting, such like high pressure sodium lamps, which is more mature in technology. In Lianyungang, it is possible for street lights (250W high pressure sodium lamps) that made by OSRAM and GE can normally maintain a 5-year work without any problems. If taking the price factor into consideration, then there may not be much of an advantage to using LED street lights.

 

Some people may ask: how about the applications on highway? What are the advantages of LED lights and high pressure sodium lamps relatively in this area? “Currently, LED technology is still in the continuous development. Many technological bottlenecks have not been solved that. Nowadays the integrity and normalization of highway LED lighting has no effective solutions. Pilot applications are feasible, but had better not been used in large-scale applications.” said Mr. Tao Zhang.

The improved structures of OLED devices

Normally, OLED devices will have relatively complex constructions to obtain higher energy efficiencies. However, these complex constructions intangibly increase the costs of production. The simplified structure can dramatically simplify the production process of OLED devices and thus have significant influences on the promoting of OLED. The simplified structure was firstly invented by J. Meyer and his colleagues in 2007. They created a simplified green phosphorescent device that has two organic layers, the efficiency of which can reach up to 40lm/W under 100cd/m2. In 2011, professor Z. H. Lu and his team found that ITO surface that after chlorine treatments can increase the power function to 6.1eV. In this way, extra HIL and HTL can be omitted, and consequently simplify the design and producing of OLED.

 

Normally, OLED devices will have relatively complex constructions to obtain higher energy efficiencies.

 

Tandem structure: Stephen R. Forresh suggested in a recent published report that using MoO3 in white phosphorescent devices as the connecting layer. The total efficiency is 22.7lm/W. M. V. Madahava Rao suggested to use pentacene/C60 PHJ as the connecting layer of tandem. Connecting layers used this material have better luminousness, weakening the effect of microcavity.

 

SPP enhanced OLED structure: 20%-40% light generated by OLED devices will be restricted in SPP. If the metal surface has similar construction as nanostructure, the restricted light can be sent out from SPP. A. Krumar created a layer of gold clusters of the surface of OLEDs through vacuum evaporation. Applying this technique in phosphorescent devices can increase the light efficiency by 2.8 times. A. Fujiki used special chemical method to form a thin layer of gold nano-particles on the surface of ITO, then deposited CuPc on the HTL. The thickness between metal and the light-emitting layer is adjustable. In theory, the light intensity can be increased by 20 times.

 

Quantum dots used on the OLED applications: Chang-Ching Tu and his colleagues used electrochemical etching methods to create silicon quantum dots, and proved that the silicon quantum dots (which should generate Blue-rays) usually sent out red rays due to Stokes shift caused by surface oxidation. In the “Solid State Project” of US Department of Energy, QD Vision created the enhanced quantum dots substrate for OLED solid state lighting and led lights, which can increase the light efficiency from 60% to 76%.

Working principles of OLED technology

Organic Light-emitting Diodes (OLED), is a new kind to light-emitting component based on semiconductor technology. OLED have many advantages: solid state, active light emitting, high contrast, super thin, low power consumption, no angle restriction, fast respond, wide working temperature range and wide area, etc. Contributed by these advanced properties, OLED technology can not only be used in display area, but also in lighting industry. Many experts believed that once OLED will be a good replacement for LED as the technology matures. In this article we will give a small talk about the global OLED industry.

 

Organic Light-emitting Diodes (OLED), is a new kind to light-emitting component based on semiconductor technology.

 

The earliest development of OLED can be traced back to the 1930s, Dr. Destriau dispersed organic fluorescent compounds within polymers to obtain the first electroluminescent device. But not until 1987, when Tank C W from Kodak created the first OLED (based on small molecule fluorescent materials), this technology has been used in real applications. In 1990, Friend and Burroughes from the University of Cambridge developed a new compound based on OLED technology and named it as polymer OLED (PLED led lights).

 

OLED has a typical sandwich structure of an organic semiconductor layer between two electrodes. Positive electrode are made of ITO, which is a thin and transparent materials that with similar properties as semiconductors. The negative electrode normally used Ca, Al as materials, for the reason that these materials have lower power functions. When voltage applied on both side of electrodes, the organic semiconductor layer will be stimulated and generated photons. The color of rays all depend on the materials that used, usually there are red, green, blue and white rays. In order to obtain higher performance, scientists may add multiple layers within the semiconductor layer, such like holes injected layer (HIL), holes transmit layer (HTL), electron transmit layer (ETL), and electron injected layer (EIL).

 

According to the different organic film materials used in the carrier transporting layer and the light emitting layer, OLED also can be divided into small molecular OLED and macro-molecular OLED. According to different driving method, OLED also can be divided into passive (passive matrix) OLED and active (active matrix) OLED.

 

According to the principle of OLED technology and production process, the entire OLED industry chain can be divided into equipment manufacturing, materials, driver modules, panel and device manufacturing.

How to improve the light efficiency of low-power LED lights?

How to improve the light efficiency of low-power LED lights? It was always a big challenge for LED lighting industry. Recently, researchers from MIT have created a new conversion device that can let LEDs generate more optical energy even higher than electrical energy they consumed. In other word, this new conversion device can increase the current light efficiency of LEDs to more than 100%. This invention made low-power LED lights emitting highly brightness light become feasible.

 

How to improve the light efficiency of low-power LED lights?

 

The working principle of LEDs is converting electrical energy into optical energy (emit light). Currently, a large number of experts and scientists are applying themselves to finding effective methods to create highly bright but more efficient LED lamps. One of the biggest obstacles to that is increasing the power consumption will lead to the reduction of light efficiency. According to the explanation of researchers from MIT, instead of increase the power consumption, they decline the input voltage dramatically. By calculation, when input voltage is cut into half, the power consuming will be dropped by 4 times. Simultaneously, the light efficiency will stably increase by 2 times. It is cleared that the dropping of power consumption will giving rise to the light efficiency.

 

During the tests, researchers dropped the consuming power to only 30pW, but measured the optical energy as high as 69pW, which gave out a light efficiency of 230%. When external voltage is applied on LEDs, holes and electrons within LEDs will be combined to generate photons. However, this combination occurred with a certain possibility. Unlike other researchers, scientists from MIT did not concentrated on this point to attempt to increase the light efficiency by raising this possibility. Instead, they made use of the tiny amount of heat caused by atomic lattice vibrations within equipments to generate more electrical energy.

 

This heat-utilized light-emitting method can cool down the working temperature of LEDs during the operation, which can also be considerate as a part of the cooling section. Under ambient conditions, this kind of cooling may have ignorable effects and very little practicality. It may probably be used in designing of heat-free lamps. When used as a heat pump, the device can contribute to solid-state cooling applications, like generators.

Price war of LED lights is a double edged sword

Many business-related people, either merchants or CEO from giant enterprises, in many conditions, they have to admit that the price war is an invincible magic weapon to capture the market, but it will bring huge losses as well. However, what happens next? Growth or elimination? Taobao is a successful case. After holding the market (almost), Taobao started to collect all kinds of fees which higher than state standards. But this situation is very rare. In most cases, merchants will be end in death, eliminated forever. LED lighting technology has been developed in China for only 10 years. Theoretically it is an emerging and immature market, full of opportunities but also challenges. Although price war of LED lights is a double edged sword, but it is inevitable, just like certain fixed theorem for the market.

 

Many business-related people, either merchants or CEO from giant enterprises, in many conditions, they have to admit that the price war is an invincible magic weapon to capture the market, but it will bring huge losses as well.

 

Competitions in the market is cruel, Taobao’s experience is non-repeatable. It is cleared that for most media and small sized companies, price war of LED lights can only cut down your income furthermore, Taobao is just a legend. Maybe people doing business in LED lighting industry should pay more attention on NVC, which has been seen as a successful example in this area. It has been proved that LED market development should start from projects, followed by retails (including specific shops and online shopping). However, no matter what method you are taking, earning money is the most important thing. Then someone my asked, how to make money among such intense competitions? How could I survive and finally success in an emerging industry? Occupying channels is an essential point. There are countless articles online about LED marketing channels: concentrating on management and reducing costs, concentrating on technology and applying for patents, focusing on the minority of personalized products. If you have adequate strength to pump prime, you can focus on each point mentioned above.

 

Price wars were always end up with injuries of everyone. Only those giant companies with abundant fund and advanced technologies can service in the end. The start of LED lighting market will be a long induction period, after which is the sudden coming outbreak period. Outbreak will not be last long (several years maybe). Then LED lighting market will enter the long period of downfall. Replacements will quickly emerge in the market, such as OLED lamps. When you spend most of your money and your energy on price war of LED lights and success finally, you will find out that the “prime” of LED lighting industry has passed. It is a double edged sword

Advantages of LED car lighting applications

In spite of various problems, such like expensive costs, heat dissipation problems, technical difficulties, automotive manufacturers still strived to introduce LED car lighting applications. The main reason is this new lighting source can unprecedentedly make vehicle lighting design more flexible. It is even possible for consumers to customize their automotive style. In addition, the light efficiency of LED lights has already been able to match with HID lamps. Therefore, it is highly hopeful that LED can surpass other existing lighting technology and dominate car lighting market.

 

In spite of various problems, such like expensive costs, heat dissipation problems, technical difficulties, automotive manufacturers still strived to introduce LED car lighting applications.

 

According to the product manager of Cadillac Escalade Platinum, the light distribution spectrum of LED is closed to natural light, making the reflecting efficiency from objects (such as road traffic instruction signage / line) be much higher than other lighting sources. Thus drivers can observe from a far distance and we take an early respond.

 

The temperature color of LED car lighting applications is around 5500K-6000K, whiter than other car lamps (HIP lamps that send out light blue rays have temperature colors around 4000K and halogen lamps send out yellow rays have temperature colors around 3000K). Therefore, in the optical design of HID lamps, scientists usually shifted the blue rays in the spectrum to the edge of emission spot, which places drivers rarely took notice of, in order to reduce the uncomfortable interference caused by colored rays.

 

But for oncoming drivers, still will be interfered by Blue-rays in the marginal area, causing dazzling and consequently increasing the risk of accidents. In the anti-glare aspect, high-power LED lamps (large LED lamps) have big advantages: not only provide sufficient comfort for the owner, but also keep nearby drivers from visual interference. Since Toyota Lexus applied different lighting sources on dipped headlights (LED lighting technology) and high beam lights (halogen lighting technology), owners of LS600h may interfered by color difference during the switching.

 

In a word, according to Mr. Asif Anwar from the marketing research and consulting department of Strategy Analytics: although LED car lighting applications are in the very early stage of development, the market has huge potentials. It is expected that, by 2012, the market of LED car lamps will reach up to 80 million dollars. LED will become the new darling of the automotive lighting industry due to its advancing in security, reliability, energy efficiency and ease of aesthetic design.