Improving color rendition in solid state white lighting through the use of quantum dots

Abstract

Quantum dots have the potential to be used in solid state white lighting applications as an additional down-converting component to better represent wavelengths in the red spectral region, leading to higher quality white light with improved color rendering. In this contribution, we report on color characteristics of phosphor-converted white light-emitting diodes that utilize inorganic garnet-based phosphors, with quantum dots incorporated appropriately. Devices were fabricated using red-emitting CdSe/ZnS core/shell quantum dots (λ_em = 560 nm or λ_em = 590 nm) in conjunction with yellow-emitting Y₃Al₅O₁₂:Ce³⁺ or green-emitting Lu₃Al₅O₁₂:Ce³⁺ and a blue-emitting InGaN LED (λ_em = 450 nm). Several phosphor/quantum dot geometries were examined, including encapsulating the phosphor powder and quantum dots together in silicone resin, or in two separate layers of silicone resin, with either the quantum dots closest to the LED or the phosphor particles closest to the LED. The quantum dots were most efficient when encapsulated with the phosphor particles in the resin. Devices with Y₃Al₅O₁₂:Ce³⁺ and quantum dots (λ_em = 590 nm) achieved a correlated color temperature of 4000 K, color rendering index of 81, and luminous efficacy of 57 lm W⁻¹, while devices with Lu₃Al₅O₁₂:Ce³⁺ and quantum dots (λ_em = 590 nm) achieved a correlated color temperature of 5700 K, a color rendering index of 90, and luminous efficacy of 22 lm W⁻¹. The results obtained suggest that the use of quantum dots may allow for solid state white lighting devices with high color rendition.