Intelligent LED to achieve better lighting and data transmission performance

RenssELaer Polytechnic Institute (RPI, New York, Troy) researchers published their research progress in light-emitting diode (LED), can greatly improve the performance of LED lighting and energy efficiency. They with Samsung motor (Samsung Electro-Mechanics, Suwon city) to develop the polarization matching LED, the lighting output increased by 20%, while the conversion efficiency of LED parameters characterization, electro-optical conversion efficiency of 25%.

The new device significantly reduces the efficiency of the settlement, which is the main factor limiting the efficiency of LED devices. It is well known that when the low density current flows through LED, its efficiency is the highest. However, some applications, such as higher light bulbs, need to use high power devices, so that LED will lose efficiency. Although the principle of efficient deposition is not fully understood, some studies have shown that a large part of the reason is due to the leakage of electrons.

"In the past two years, this problem was of widespread concern; the main obstacle is also a solid state lighting technology in the application of the" Fred Schubert in charge of the research project, he is also a professor at Rensselaer, and the National Science Foundation (NSF) funded by the director of Engineering Research Center of intelligent lighting.

"We trace the process of electrons escaping from the active region of light emission. In the active region, we hope that the electrons remain in the hole so that they can recombine and emit light. However, if the carriers leave the active region, there will be no recombination. We believe that this is the source of the efficiency of the deposition: one of the carriers out of the active area, which forms the active area of leakage. "

Due to the current high brightness LED are working in the high current density range over the peak efficiency, so this phenomenon is very common. The natural idea is to reduce the current density to the peak efficiency area, but its brightness is not acceptable, so this problem has become a huge obstacle to LED applications.

Other researchers have tried the electronic barrier, but the results are not satisfactory. PRI's research group, a group of academics, industry partners and students, uses the concept of polarization matching. They use the quadrupole material in the active region, and the polarity of the polar materials is reduced by using different methods.

The new LED has a new design of polarity - matching the active region, allowing the device to obtain peak efficiency in the high current density region. They studied the active region of light in the LED, and the researchers found that the material inside the polar mismatch is likely to be an electron leak, which is why the efficiency is reduced. More studies have shown that by using different quantum barrier designs, the polarity mismatch can be greatly reduced. Replacing the GaInN/GaN layer of the LED active area with the traditional GaInN/GaInN. A more matched polarity can be obtained, which reduces the electron leakage and the efficiency settling.

The band diagram of the GaInN/GaN active region and the new polarization matched GaInN/GaInN active region in LED. (source: Rensselaer Polytechnic Institute)

"Nitride is a special kind of semiconductor, unlike silicon and gallium arsenide," Schubert said. "Gan has a high internal electric field, which is a problem. Our polar matching structure is just on the C plane sapphire substrate, which can greatly reduce the electric field in the active region. As a result, the efficiency of deposition is restrained, the output power is increased by about 20%, and the conversion efficiency is increased by about 25%. For the LED industry, this is a very surprising figure. In order to improve the efficiency by 5%, the industry is willing to make any effort; the 20% is very great improvement. "

Schubert pointed out that the single reason for the efficiency of the settlement, academia has not yet agreed. "The next step is to find out the physical reasons behind them, and to completely eliminate the causes of the efficiency of the settlement. "The research team will continue to explore other possible LED structures that can further improve the device. According to Schubert, LED can also achieve other additional features, such as the change of luminous performance, similar to the sun's color and temperature, so you can get closer to the natural full spectrum lighting.

"We can modulate the spectrum," he said. "This allows for a natural, adjustable light source that can be used to process data. This is one of our goals: the production of light and the dual function of processing data. Imagine, traffic lights, lights on the airport terminal, in addition to the lighting function, can also be used for communication; the buildings with light source and room number information, can track objects in the building. Intelligent light source can achieve all this. This is our long-term goal. Schubert expects, with health care, transportation systems, digital display and computer networks, based on LED and solid-state lighting lighting devices can set off a new round of environmental protection, energy saving and low cost wave.