Research & Reviews: Journal of Engineering and Technology
MenuISSN: 2319-9873
ISSN: 2319-9873
+44 7456 035580Leelakrishna Reddy
University of Johannesburg, South Africa
Keynote: RRJET
In this review we will present a number of research papers pertaining to white colour emission from Dy3+ doped and undoped phosphor materials. The search for a single component phosphor material that could deliver high quality white light under UV or near UV excitation is an area of active research for commercial purposes. Amongst all rare earth elements Dy3+ is the only ion that deliver simultaneosuly blue and yellow light under UV excitation. In optimising the Yellow/Blue emission intensity ratios, white light can be realized. Dy3+ (4f9)displays approximately 4 emission peaks at around 480nm, 575nm, 670nm and 758nm corresponding to transitions from the metastable 4F9/2 state to various lower states such as 6H15/2 (blue), 6H13/2 (yellow), 6H11/2 (red) and 6H9/2 (brownish red), respectively. In general, the hypersensitive transition at 6H13/2 (yellow) is electric dipole in nature becomes prominent only when Dy3+ ions are positioned at low symmetric sites with no inversion symmetry in the host matrix. On the other hand, the blue magnetic dipole transition at 6H15/2 becomes prominent only when Dy3+ ions are positioned at highly symmetric sites in the host material with inversion symmetry. Despite the white colour emission from the Dy3+ ions, these transitions are mainly associated with parity forbidden 4f -4f transitions, the white produced maybe diminished at times, hence the need to include a sensitizer to bolster the forbidden transitions experienced by Dy3+ ions. In this review we will focus on the variability of the Yellow/Blue emission intensities in different host materials from Dy3+ ions (doped or undoped) by studying their photoluminescent properties (PL), their CIE chromaticity coordinates and correlated colour temperature (CCT) values for white colour emissions that is adaptable to different environmental conditions.
Prof Leelakrishna Reddy obtained his PhD in Physics from the University of Johannesburg, South Africa. He has supervised a number of PhD and MSc students in Nano phosphor materials for white LED applications. He has published more than 70 peer reviewed articles in reputable journals. Further, he has delivered a number of Keynote lectures and Invited Talks at various Nano conference around the world.