White Light Emission by Dy3+ Doped Phosphor Matrices: A Short Review

Abstract

In this review we have studied number of research papers related to white light emission from Dy3+ doped different host matrices. It is observed that most of the Dy3+doped aluminates, silicates, borates etc., emitted blue, green and red colour with specific intensities so that CIE coordinates, appeared near to white light. Correlated Colour Temperature(CCT) values of these phosphors expressed that the white light emission produced, was adaptable to human eyes. Dy3+ ions act as activator in each case. Four peaks at approximately 480,575, 670, and 757 nm could be seen in most of the Dy3+ doped phosphors. Expected transition responsible for these peaks are 4F9/2 → 6H15/2 (Blue Colour), 4F9/2 → 6H13/2 (Green-Yellow Colour), 4F9/2 → 6H11/2 (Red Colour) and 4F9/2 → 6H9/2(Brownish Red Colour). Few of the discussed phosphors exhibited long phosphorescence, starting from several minutes to few hours. Mechanism responsible for long lasting white light emission was also discussed. Five different factors, to recognize the phosphors for its suitability as commercial white light phosphor have been discussed.

Theory and Calculation of the Phosphorescence Phenomenon

“…In great contrast, the absorption or emission involving singlet and triplet states (T n ) are strongly spin-prohibited since they proceed as second-order, or nonlinear, processes involving both spin–orbit and dipole couplings. A large body of phosphorescence measurements has been accumulated over the years, covering simple diatomic molecules and more complicated compounds like polyacenes, − porphyrins, ,, circulenes, , heavy metal complexes, − , and others. − Despite this fact, investigations on phosphorescence at the level of modern quantum mechanics are quite limited and a detailed description of phosphorescence mechanisms has therefore remained elusive …”

Electronic Energy Levels of Dysprosium(III) ions in Solution. Assigning the Emitting State and the Intraconfigurational 4f–4f Transitions in the Vis–NIR Region and Photophysical Characterization of Dy(III) in Water, Methanol, and Dimethyl Sulfoxide

“…Dysprosium­(III) ions exhibit coordination chemistry similar to that of other lanthanide­(III) ions of similar size, yet it is significantly less explored. − The solid state luminescence properties of dysprosium­(III) are already relatively well-understood, and the NIR transition of Dy­(III) has been exploited in telecommunication. − The pale blue visible luminescence has found use in lighting, where single-component white-light emitters need blue to add to green and red pigment. − …”

White light emitting thermally stable bismuth phosphate phosphor Ca3Bi(PO4)3:Dy3+ for solid‐state lighting applications

“…This approach provides better CRI and CCT but increases the synthesis processing time and cost of the device. Furthermore, this approach also suffers from certain drawbacks such as phase separation, reabsorption of blue light by green and red phosphors, poor RGB color mixing, and low color stability owing to the different emitting centers or phosphors . To overcome the aforementioned problems, development of a single‐phase white light emitting phosphor is very important and has gained significant attention in comparison to RGB phosphors in the area of solid‐state lighting …”

“…Furthermore, this approach also suffers from certain drawbacks such as phase separation, reabsorption of blue light by green and red phosphors, poor RGB color mixing, and low color stability owing to the different emitting centers or phosphors. 12,13 To overcome the aforementioned problems, development of a single-phase white light emitting phosphor is very important and has gained significant attention in comparison to RGB phosphors in the area of solid-state lighting. 14,15 The white light emission can be obtained in single host lattice either by doping of single rare-earth (RE) or multiple RE ions in the appropriate host.…”