At the seminar "Green Device Forum 2010", which was held concurrently with the "Green Device 2010" exhibition, the "New Generation Lighting Forum" for solid-state light source technology such as LED , organic EL and semiconductor lasers was held. The domestic and foreign manufacturers in the field of solid-state light sources have introduced the latest developments in terms of luminous efficiency, brightness, lifetime, color rendering, surface light source and point source.
Japan's Philips Lumileds Lighting's Shenshan Bosuke is focusing on the future of related technologies, centering on the high efficiency of white LEDs. According to Shenshan Boxing, according to the improvement speed of ordinary white LED luminous efficiency, it will exceed 200lm/W in recent years. Although the bulb color LED is inferior to the ordinary white LED in terms of luminous efficiency, it has reached 90-100 lm/W and will soon exceed 200 lm/W. In the future, it is also necessary to achieve the same level of high efficiency at high current densities. The specific approach is to reduce the "Droop" phenomenon with higher current density and lower luminous efficiency.
In order to solve this problem, Philips Lumen of Japan is changing the structure of the blue LED chip , which is the light source of white LED and bulb color LED. Although specific details have not been disclosed, a layer structure for preventing accumulation of electrons or holes has been employed in the vicinity of the interface between the quantum well layer and the barrier layer in the light-emitting region of the blue LED chip, so that electrons and holes are easily recombined. In this way, the external quantum efficiency of the 1mm square chip can reach 65.5% when the current is 350mA, and the efficiency can reach 59% when the current is 1A.
By the above method and the technique of reducing the forward voltage, it is desired that the luminous efficiency at a current density of 2 A/mm 2 in a 1 mm square chip can reach 150 lm/W, and the luminous flux can reach 1000 lm. This requires an internal quantum efficiency of 80% (currently 53%), an external quantum efficiency of 72% (currently 47%), and a phosphor conversion efficiency of 252 lm/Wopt (currently 228 lm/Wopt). .
Japan and Europe OSRAM Opto Semiconductors (Osram Opto Semiconductors GmbH) is also introduced to reduce Michael Schmitt recession high output power white LED technology. This is a technique called "UX: 3" where the n-electrode is placed inside the LED. The current is passed evenly inside the chip to control the current density and improve efficiency. In addition, by eliminating the electrodes on the surface of the chip, the light inside the chip is more easily released to the outside of the chip.
The company revealed the characteristics of the optical output power when a current is applied to a chip of 1 mm square. Compared with the ideal characteristic (no decay phenomenon) in which the optical output power increases linearly with increasing current, the optical output power when the current is in the range of 350 mA to 1 A is about 15% lower than the ideal characteristic.
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