Puja Kumari

Bio: Puja Kumari is an academic researcher from Indian Institute of Technology Dhanbad. The author has contributed to research in topics: Phosphor & Photoluminescence. The author has an hindex of 7, co-authored 9 publications receiving 170 citations.

Structural, optical and special spectral changes of Dy3+ emissions in orthovanadates

Abstract: This paper reports on the structural, optical and photometric characterization of yttrium gadolinium orthovanadates (Y1−xGdxVO4) doped with Dy3+ for white emission in solid state lighting. A series of orthovanadates were prepared through a low temperature co-precipitation method and further post annealed. The as synthesized phosphor particles revealed a single phase tetragonal structure with space group I41/amd(141). The infrared spectra confirmed the presence of characteristic vibrational bands of orthovanadates. The microscopic images showed elongated particles after annealing and the particle sizes were estimated in the range of 10–50 nm. The band gap of the prepared phosphors, calculated from the corresponding diffuse reflectance spectra was observed to be 3.75 eV and 3.57 eV for YVO4 and GdVO4 respectively. Y1−xGdxVO4:Dy3+ phosphors, illuminated with ultraviolet light exhibited characteristic blue and yellow luminescence corresponding to 4F9/2 → 6H15/2, 4F9/2 → 6H13/2 transitions of Dy3+ ion. The emission spectra showed the variation in the intensity ratio (Y/B) with Gd3+ ion variation. Furthermore the thermal quenching property, decay analysis and photometric characterizations were also studied in detail and the results indicated the suitability of these phosphors in solid state lighting.

Influence of Dy 3+ ions doping on structural and luminescent properties of GdVO 4

Abstract: Herein, the effects of Dy3+ doping concentration on the structural and photoluminescence properties of Dy3+ activated tetragonal GdVO4 matrix, synthesized via the co-precipitation method, have been presented in detail. The infrared spectroscopic studies confirmed the presence of vibrational bonds corresponding to Gd-O at 433 cm−1 and V–O at 830 cm−1, respectively. The microscopic studies elaborated nanosized spherical particles. Upon UV excitation, the as-prepared GdVO4: xDy3+ samples exhibited intense blue and yellow emissions due to 4F9/2 to 6HJ (J = 15/2, 13/2), respectively. The dominant peak at 574 nm was due to hypersensitive electric dipole transition 4F9/2 → 6H13/2 (∆J = 2) of Dy3+ ions. Above 1 mol% of doping, the quenching in PL intensity was observed due to inter ionic energy transfer among Dy3+ ions. The non-radiative energy transfer between Dy3+ ions was attributed to multipolar interactions. The critical distance of the energy transfer was calculated to be 25 A. Photometric characterizations confirmed its applicability in solid state lighting and display.

Quantum Dots for LED Downconversion in Display Applications

Abstract: Quantum dots (QDs) are now on the verge of widespread adoption in display applications, after 25 years of scientific research and over a decade of commercialization efforts. This is the result of a combination of industry trends such as liquid crystal displays (LCDs) and light emitting diode (LED) backlight units (BLUs), combined with improvements in QD performance and manufacturing that have taken place across the growing QD ecosystem of Universities, National Labs, and private and public companies. As QDs emerge as a viable choice as downconversion materials in LED backlit LCD displays, they have the potential to be employed in several geometries within these otherwise similar display systems. In all geometries, QD LCDs will provide the broadest available color gamut to the user, in addition to potential benefits in power efficiency, brightness, and contrast. This work will summarize QD properties and advantages in such LED backlit LCDs relative to other competitive downconversion materials, as well as compare and contrast the three primary geometries that will likely be explored during the pursuit of a potentially dominant design.