A thin optical reflector is often introduced to the backside of the standard mesa type\nlight emitting diode (LED) chip with the aim to enhance its light output. However,\nmost of the reported light output enhancements because of backside reflector (BR)\nintroduction might not be relevant. This is because the reported measurement is\noften from a naked LED chip instead of a packaged LED emitter, and those based\non the packaged emitters employing conventional silver based die attach adhesive\n(DAA). The actual role of BR, which is expected to be greatly influenced by the\npackaging materials and processes, is investigated for the monotonic blue color\nand white LED emitters using Monte-Carlo simulations. Contrary to prior reports, it\nis demonstrated for the first time that the role of BR can be diminished when the\noptically transparent DAA is used and other key packaging materials and processes\nare optimized, i.e., the light output for a packaged emitter with a BR-free chip can be as\nhigh as that of the packaged emitter using the same chip but with an added BR.
Loading....