Optical characteristics and longevity of quantum dot-coated white LED

Abstract

For improving the light quality of a white LED, the feasibility of QDs was seriously considered and their longevity as well as efficiency was evaluated. For that purpose, the most similar combination of phosphors to the commercial light-converting system was selected and fabricated as the hybrid phosphor of Lu3Al5O12:Ce3+ and CdSe/ZnS QDs in remote type. To ensure competitive, a frame of reference with Lu3Al5O12:Ce3+ and (Sr, Ca) AlSiN3:Eu2+ was made and two cases were compared. When the hybrid phosphor with QDs was used, it was found that the luminous flux was increased by 20%, compared to the conventional combination of inorganic phosphor in commercial level. Also, CRI value can be controlled up to 90. But, the LED PKG reliability of a white LED with QDs in remote type still needs to be improved. The luminous flux of the hybrid phosphor with QDs was decreased to 91% within 1000 hours under the operating condition of 85 degrees C and 85% of relative humidity, while that of conventional combination of inorganic phosphors was kept in stable luminescence. Substantial variation of color coordinates were observed. By tracking the changes of the R9 value over the time, it was found that the quantum structure had not been sustained during the operation. More work on the stability of QDs in phosphor plate should be done for device application. (C) 2014 Optical Society of America