| 초록 |
In recent years, there has been a growing focus on research in the area of white light-emitting-diodes due to their merits of being highly efficient and having a longer lifetime. Reliability issue has been mainly focused on the degradation of the chip material; however the mechanisms of degradation and the limitations of packages are also not well understood. In this study we have explored the effect of various types of phosphors i.e. LUAG (green, Lu3Al5O12:Ce3+), Silicate (yellow, Sr2SiO4:Eu2+), CASN (red, CaAlSiN3:Eu2+), Oxynitride (yellow, (Sr,Ba)Si2O2N2:Eu2+) on reliability/degradation of remote phosphor in glass (PIG) encapsulants for white LEDs. For this purpose, glass composition: SiO2-B2O3-ZnO-N2O was mixed with each phosphor type separately and then sintered at appropriate temperature to get PIG. The reliability of these phosphors in single glass matrix is evaluated by sequential damp heat (85oC/85RH) test which last for 1000 h. Luminous loss, and shift in CIE coordinates of PIGs were measured after the subject conditions. Surface features were analyzed using scanning electron microscope and energy dispersive X-ray spectroscopy. Thermal- or moisture induced quenching behavior was also analyzed. Surface of PIG with different phosphor has degraded differently in terms of structural properties and oxidation on the surface under same exposure. Analyzing PIG surface degradation mechanism can help to increase lifetime of LEDs. |
