Recently, as the Reuters, University College Cork, Turkey (? Ko University) researchers have demonstrated a white light emitting diode (LED) based nanomaterials, it creates a light emission efficiency records: 105 lumens / watt. Further developed, the new LEDs achieve efficiencies of up to 200 lumens per watt, making them a promising energy-saving light source for homes, offices and TV stations.
background
LED (Light Emitting Diode), a solid-state semiconductor device that directly converts electricity into light.
Flexible LED developed by the Finnish National Technical Research Center
The basic principle of LEDs is to emit visible light when electrons and holes recombine. The core component of the LED is a semiconductor wafer. The wafer consists of two parts: a part is a P-type semiconductor and a part is an N-type semiconductor. When the two semiconductors are connected, a "PN junction" is formed. When a current is applied to the wafer, electrons flow to the P region and combine with the holes, and then emit energy in the form of photons.
However, the color of the luminescence, that is, the wavelength of the light, is determined by the material from which the PN junction is formed. Generally, a gallium arsenide diode emits red light, a gallium phosphide diode emits green light, a silicon carbide diode emits yellow light, and a gallium nitride diode emits blue light.
Innovation
Recently, researchers at Ko? University in Turkey demonstrated a white light-emitting diode (LED) based on nanomaterials, which created a record of luminous efficiency: 105 lumens per watt. Luminous efficiency is the ratio of luminous flux to power, which is a measure of the efficiency with which a light source uses electricity to produce light. Through further development, the new LEDs can achieve 200 lumens/watt efficiency, making them a promising energy-saving light source for homes, offices and TV stations.
Quantum dot white LED
In the Optics, a high-impact research journal of the Optical Society of America, researchers describe how they created this highly efficient white LED. The new LEDs use commercially available blue LEDs combined with flexible lenses filled with nano-sized semiconductor particle (quantum dot) solutions. The light from the blue LED causes the quantum dots to emit green and red light, combined with blue light to create white light.
Flexible lens
technology
To create white light from existing LEDs, the researchers applied a blue-yellow phosphor-based coating to the blue LED to combine blue and yellow light. Because the phosphor has a wide range of emission, from blue to red, it is difficult to tunate the resulting white light characteristics sensitively.
Unlike phosphors, quantum dots produce a pure color because it emits only a narrow spectrum. This narrower emission combines quantum dots that produce different colors of light with blue LEDs to create high quality white light with precise color temperature and optical properties. Quantum dots also have the advantage of being easy to manufacture, and their luminescent color can be varied by increasing the size of the semiconductor particles. Further, by changing the concentration of the quantum dots incorporated, it is convenient to generate a warm white light source like an incandescent lamp or a cool white light source like a fluorescent lamp.
Although quantum dots currently embedded in thin films are used in LED televisions, such illumination schemes are not suitable for widespread use in general illumination. By shifting quantum dots in liquids, researchers have overcome the problematic efficiency degradation that occurs when nanomaterials are embedded in solid polymers.
Manufacturing efficient white LEDs requires quantum dots to efficiently convert blue light into red or green light. The researchers conducted more than 300 synthetic reactions to resolve optimal conditions, such as temperature and reaction time, to create quantum dots that emit light of different colors while exhibiting optimum efficiency.
Sedat Nizamoglu, a leading researcher at the school, said: "The production of white light requires the integration of the right amount of quantum dots, and even if this is done, it will require a myriad combination of blue, green and red light to produce white light. We have developed a based on our recent The simulation of the theoretical solution is reported and used to determine the appropriate amount, as well as the optimal quantum dot color combination, to efficiently generate white light."
In order to manufacture new LEDs, the researchers used a quantum dot solution of cadmium, selenium, zinc, and sulfur mixed under high temperature conditions to fill the space between the polymer lens and the LED chip. The researchers used a silicone resin to make the lens because the elasticity allowed it to inject the solution into the lens without any leakage, and the transparency of the material ensured that the necessary light could pass.
The researchers demonstrated that their liquid-based white LEDs can achieve twice the efficiency of solid-film quantum dot LEDs. They also demonstrated by using a white LED to illuminate a 7-inch display.
Nizamoglu said: "Quantum dots are very promising for efficient lighting applications. There is still a lot of room for technology development for generating more efficient lighting solutions."
value
Nizamoglu said: "Efficient LEDs have the potential to save energy and protect the environment. Replacing traditional light sources with LEDs with a luminous efficiency of 200 lumens per watt can reduce global lighting power consumption by a factor of two. This reduction is equivalent to 230 The typical 500 MW coal-fired power plant will generate 200 million tons of greenhouse gas emissions."
He added: "Our new LEDs achieve higher levels of efficiency than other quantum dot-based white LEDs. This quantum dot and new LED synthesis and manufacturing solutions for quantum dots and new LEDs, It's simple, cheap, and mass-produced."
future
Next, researchers are working to improve the efficiency of LEDs and want to achieve high levels of efficiency with environmentally friendly cadmium-free and lead-free materials. They are also planning to study liquid LEDs under different conditions to ensure they are stable for long-term applications.
Editor: Yan Zhixiang
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