Hybrid Down-Converting Structures for Solid State Lighting
Achieving higher luminous efficacy in phosphor converted light emitting diodes (pcLED) requires breakthroughs in down-converting materials that provide high conversion efficiency, tunable narrow bandwidth emission, and temperature/chemical stability. While conventional bulk phosphors are currently the dominant down-converters used in high power solid-state lighting (SSL) applications, their performance is limited by intrinsic properties such as high scattering cross-sections and large emission bandwidth. On the other hand, conventional luminescent nanocrystals (e.g, quantum dots or QDs) have high self-absorption and poor thermal and chemical stability for HB LEDs. Ultimately, these materials will enable a new generation of solid state lighting devices with high luminous efficacies, high color and thermal stability, and with spectral efficiency near the theoretical maximum luminous efficacy of radiation (LER), as a result of their color tunability and narrow bandwidths (FWHM < 30nm).