Research On LED High Efficiency Cooling And Optical Design

LED（light emitting diode） is a new type of lighting source afterincandescent lamp,fluorescent and high-intensity discharge lamps for itsadvantages of high efficiency, environmentally friendly and low-cost. With theimproving of luminous efficiency and applied technology, large-size LCD TVbacklight, automobile, commerce and industrial lighting have gradually becomethe main application areas of LED.At the same time, the requirements of thepeople on LED luminescence properties are increasing. Therefore, how toprepare the high-performance LED has become a hot spot. Even though the LEDtechnology has had a rapid development, there are several factors to restrict thedevelopment of high power LED. For example, heat dissipation and lightdistribution are the most important issues, while color index is also a urgent needto improve.In this paper, we focus on the problems of heat dissipation and colorrendering index. In the respect of heat dissipation, we study the integratedpackaging technology without bracket that the chip is packaged on Al directly.Then heat is transfered to Al substrate more easily which reduces other thermallink. Therefore, heat dissipation is more effective which is a good method tosolve the problem of high power LED.In the high power LED color rendering index, we study the luminescent andexcitation spectrum of the DCJTB which is coated to the LED chips, then theYAG phosphor on top of DCJTB. Its proportion is0%、1%、2%、3%、5%and10%. It is found that yellow YAG: Ce³⁺phosphor mixing DCJTB can improvethe luminescent properties and there is a best mixing ratio of high power LEDcolor rendering index. Therefore, DCJTB can absorb the energy of LED chip andDCJTB has a strong absorption to the green region excited by the YAG：Ce³⁺phosphor.Through the experimental we can draw the conclusion that organic materialDCJTB can improve the color rendering index of high power LED. Therefore, we get the concept of pointing layers phosphor. First preparation of high powerLED, then we coat organic material DCJTB on phosphor. Its proportion is0%、1%、2%、3%、5%、10%. Then we study the luminescent by testing excitationspectrum. It is found that pointing layers phosphor not only can improve theluminescent properties, but also color rendering index of LED. Meanwhile, wecan avoid the absorption of DCJTB to YAG：Ce³⁺phosphor in the yellow-greenlight by pointing layers phosphor.To further study the influence of the organic thin film layer for high-powerLED color rendering index, we deposit organic material Alq₃：C545T and Alq₃on the glass by vacuum evaporation. Then irradiate organic thin film Alq₃：C545T and Alq₃by high power blue LED. Then we study the luminescent ofAlq₃：C545T to blue LED by testing excitation spectrum and the luminescenceefficiency of the organic thin film layer by comparing Alq₃：C545T andAlq₃. Theresults show that: high power LED can stimulate Alq₃：C545T generating yellowand green spectrum and the spectrum moves to white region. Therefore, organicmaterial Alq₃：C545T can improve the luminous efficiency and luminous flux ofLED significantly. Organic material C545T can effectively increase in theexcitation spectrum of the yellow green region.By the method of spin-coating，a layer of organic material MPPV dissolvedin organic solvent Tetrahydrofuran（THF）is coated on glass. The radios ofMPPV: THF are:25mg：1ml、50mg：1ml、100mg：1ml、150mg：1ml. We irradiateorganic thin film by blue and white LED. Then we study the luminescent bytesting excitation spectrum. The results show that: with the method of blue andwhite LED exciting the organic material MPPV, the color-rendering index andluminescent properties of LED can be improved significantly. Therefore, organicmaterial MPPV can absorb the energy of LED chip and has little absorption tothe green region excited by the YAG：Ce³⁺phosphor.