The development and characterization of phosphor converted led lamps for niche applications

In this work phosphor-converted light-emitting diodes (pcLEDs) were designed using both commercial phosphors and ones synthesized by sol–gel method at Vilnius university. Main objective of this work is to show the possibilities of pcLED spectral engineering by creating and characterizing prototypes for niche applications. To reach this objective three different prototypes were made: For plant growing, using Y3Ga5O12 (YGG) doped with 8.7 mol% Cr3+ (YGG:Cr) phosphor. Luminescent properties were studied by measuring diffuse reflection, photoluminescence (PL), PL excitation (PLE) and internal quantum efficiency (QE) in order to find optimal calcining temperature. YGG:Cr PL is a broad band in the far-red spectral region that peaked at about 711 nm. QE has shown a strong dependence on the calcination temperature. According to QE results 1300 °C was chosen as best calcination temperature. Using YGG:Cr phosphor powder and a commercial blue InGaN LED, a far-red – blue phosphor converted LED (pcLED) lamp with efficiency of 35% was designed and characterized. This Blue – far-red pcLED lamp can be used in greenhouses and meet the photophysiological needs of plants. For outdoor lighting applications prototypes with commercial Intematix (O5446 and O6040) and PhosphorTech (BUVOR02) orange phosphors were used. Pc-LEDs can provide better luminous efficiency of radiation (LER) and better color rendering indices (CRI) can be achieved compared to traditional high intensity discharge (HID) lamps. Thus making pc-LED based luminaires far better and can provide more visual comfort and lower circadian action for low-illuminance night lighting applications. Designed prototypes light is perceived as white because of small distances from the Planckian locus (Duv < 0.02). Evaluated CRI values are better than typical HID lamp values. Prototype with O5446 and O6040 can be called firelight because of their extra low CCTs and can provide more visual comfort and lower circadian action for low-illuminance night lighting applications. Furthermore a white light color preference prototype was created using commercial Intematix G1758 and PhosphorTech HTR620 phosphors. A two layer converter was made in order to achieve color preference spectra described in [12] enhancing the white light color rendition properties by increasing color saturation (CSI), but maintaining the same typical 2900 K CCT for halogen lamps and keeping the ratio of CSI and color fidelity indice (CFI) between 0.3 and 3 as research in [14] suggests