Probing the structure, morphology and multifold blue absorption of a new red-emitting nanophosphor for LEDs

• Published in: Journal of materials chemistry. C, Materials for optical and electronic devices Vol. 1; no. 37; pp. 5849 - 5855
• Main Authors: Mishra, Savvi, Rajeswari, R., Vijayan, N., Shanker, V., Dalai, M. K., Jayasankar, C. K., Surendra Babu, S., Haranath, D.
• Format: Journal Article
• Language: English
• Published: 01.01.2013
• Subjects: Colors (materials); Emittance; Markets; Morphology; Nanostructure; Phosphors; White light; X-rays
• ISSN: 2050-7526; 2050-7534
• DOI: 10.1039/c3tc31032a

There has been a stringent demand for blue ( similar to 450 to 470 nm) absorbing and red ( similar to 611 nm) emitting material systems in phosphor converted white light emitting diodes (WLEDs) available in the market. The conventionally used red-emitting Y sub(2)O sub(3):Eu super(3 +) phosphor has negligible absorption for blue light produced by GaInN based LED chips. To address this issue, a new red-emitting Gd sub(2)CaZnO sub(5):Eu super(3+) (GCZO:Eu super(3+)) nanophosphor system having exceptionally strong absorption for blue ( similar to 465 nm) and significant red ( similar to 611 nm) photoluminescence is presented. This is attributed to a dominant f-f transition ( super(5)D sub(0) arrow right super(7)F sub(2)) of Eu super(3+) ions, arising due to an efficient energy transfer from the Gd super(3+) sites of the host lattice to Eu super(3+) ions. The external quantum yield (QY) measured at 465 nm absorption and 611 nm emission revealed that the GCZO:Eu super(3+) nanophosphor has better QY of 23% as compared to commercial Y sub(2)O sub(3):Eu super(3 +), which is <1%. X-ray diffraction and microscopy observations showed the nanocrystalline nature and slightly elongated morphology of the sample, respectively. While the energy dispersive X-ray analysis identified the chemical constituents of the GCZO:Eu super(3+) nanophosphor, the color overlay imaging confirmed the substitution of Eu super(3+) for Gd super(3+) ions. As seen from the QY statistics it is highly anticipated that the multifold absorption at similar to 465 nm would certainly improve the color rendering properties of existing WLEDs.