Global solid state lighting technology and product development

Solid state lighting has the advantages of energy saving, environmental protection, in the global warming phenomenon is increasingly serious, for LED or lighting manufacturers used to persuade consumers to abandon the traditional lighting, solid state lighting to change the selling point. Many LED vendors have also claimed the superiority of their lighting products and the receipt of good condition. But in the current situation, the solid state lighting fixtures and traditional lamps in the price after all, there is still an insurmountable gap. In short, the author speculated that the solid-state lighting market at least 4, 5 years later, the total evaluation of price and performance can be compared with the traditional lamp, and really has a space for one person in the lighting market.

The so-called solid state lighting refers to the light emitting part of the solid (different from the fluorescent light gas), so LED and OLED (organic light-emitting diode), are solid state lighting source. Although the pace of commercialization of OLED slower than LED, but the uniformity of light, and mass production is its advantage, in the review of solid-state lighting technology progress, we should not underestimate the progress of OLED technology.

Advances in LED Technology

Review the technical progress of LED and OLED plant in the past year. First look at the progress of LED leading manufacturers nichia. Nichia released its new LED in September 2007, the experimental type products in the forward current is 350mA, luminous flux of up to 145lm, the luminous efficiency is about 134lm/W. The chip size is 1mm2, the color temperature is 4988K (in the case of If=20mA, the luminous efficiency is as high as 169 lm/W).

This new product is to use the blue LED YAG phosphors emit white light and collocation, and to enhance the efficiency of the luminous efficiency of the main factors for the progress of the Blu ray LED, Blu ray LED in If=350mA and 1A under the conditions of the luminous power were 651mW and 1.7W.

In addition to the white LED, Nichia also published new blue and green LED, the two chip size is 1mm2, under the condition of If=350mA, the luminous efficiency of blue and green LED were 80 lm/W and 109 lm/W.

Second large OSRAM Opto Semiconductors also published in September 2007 its new green LED products, the chip size of 1mm2. Under the condition that the driving current is 1A, the luminous flux is 191 LM, the luminous efficiency is lm/W, and the wavelength is 527nm. When the driving current is 350mA, the luminous efficiency is up to 81 lm/W, and the wavelength is 532nm. The new product OSRAM of the improved Droop phenomenon (Blu ray LED and green LED and InGaN as light-emitting layer LED in improving the input current density when the luminous efficiency decreases), promoted to the luminous efficiency of the products in the future will be towards the application development of LED projector light source.

At present, the high power chip on the market the main provider of CREE, also released its results in September 2007, the new experiment is a LED array (Array), composed of plural chips, the current size is 350mA, the total power consumption of nearly 8W, the luminous efficiency can reach 88~95 lm/W. The company was released in July 2006 when the LED array luminous efficiency of 79 lm/W, showing a year LED luminous efficiency increased by 11%~20%.

In addition, Cree also also issued two new high power white LED research and development achievements, one product can withstand up to 4A driving current of white LED, a cold white light up to 1050 LM, the luminous efficiency of 72 lm/W (under the same conditions can emit 760 LM warm white, luminescence efficiency 52 lm/W); another may be in the driving current of 350mA, a 136 LM (Cool White 5813K) and 104 LM (Warm White 2950K) light flux, luminous efficiency of 129 lm/W and 99 lm/W respectively. It is expected that the two prototype products can enter the production stage within two years. In terms of green LED also progress, Cree in November of the same year released its new green LED products can be issued under the 350mA drive current of 87.5 LM luminous flux.

In the high power LED packaging technology is considered to have a unique Philips Lumileds was declared in January 2007 when the high power white LED luminous efficiency has reached 115 lm/W (in the case of driving current of 350mA). In November of the same year, it published its new mass production of goods Luxeon K2, can withstand the driving current of 1A, up to 1.5A, and issued more than 160 LM light flux, LED industry is the first commercial 1A LED.

In addition to the light efficiency and can withstand the driving current efforts, to improve Lumileds for a big problem - LED lighting commercialization LED uniformity, published in August 2007, Lumiramic technology, the technology of LED can be reduced to the original color of the range of 1/4, can reduce the color temperature of each LED all the phenomenon (refer to figure 1).

Figure 1 Lumileds Lumiramic schematic data source: Philips Lumileds

Lumileds also set out the future development goals (see Table 1), the key is the internal quantum efficiency of LED luminous efficiency can be increased, especially in the high current drive Droop phenomenon, is a major issue whether LED entered the mainstream lighting application. Lumileds has proposed its explanation of Droop phenomenon and the feasible solution. But there are still many experts do not agree with the Lumileds theory, and also the vendor said they had tested Lumileds products, solutions and personally tested the proposed Lumileds, Droop phenomenon can not be improved, but the effect is not as good as Lumileds declared, the causes, mechanism and solution the Droop is still controversial.

Table 1 Lumileds high power LED Development Planning Source: Philips Lumiled

Advances in OLED Technology

Figure 2 is the technical development of OLED in the last 9 years