Enhanced visible to near-infrared quantum cutting in Tb and Yb co-doped oxyfluoride glass-ceramic
- PDF / 883,489 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 45 Downloads / 199 Views
Enhanced visible to near-infrared quantum cutting in Tb and Yb co-doped oxyfluoride glass-ceramic Z. Pan*, G. Sekar, R. Akrobetu, R. Mu, and S. H. Morgan Department of Physics, Fisk University, Nashville, TN 37208, U.S.A. ABSTRACT Tb and Yb co-doped oxyfluoride glasses were fabricated in a lithium-lanthanumaluminosilicate matrix by a melt-quench technique. Glass-ceramics were obtained by appropriate heat treatment of the as-prepared glasses. Visible to near-infrared down-conversion quantum cutting was studied for samples with different thermal annealing temperatures and time. Laser light at 488 nm was used to excite Tb3+ ions while Yb3+ ions were excited by energy transfer from the excited Tb3+ ions. Near-infrared emission at 940 – 1020 nm was observed. It has been found that the emission at 940 – 1020 nm increased significantly from the glass-ceramic compared to that of the as-prepared glass. This result suggests that the energy-transfer efficiency increases in glass-ceramics compared to that in glass. A significant portion of rare-earth ions may be incorporated inside LaF3 nanoparticles (NPs) in the glass-ceramic. Because the Yb3+ emission at 940 – 1020 nm is matched well with the band gap of crystalline Si, the quantum cutting effect may have its potential application in silicon-based solar cells. INTRODUCTION Rare-earth doped glasses are important for applications in optical devices such as scintillators, optical fiber amplifiers, lasers, optical converters of infrared radiation to visible regions, etc. In addition to the common advantages of low-cost, large-volume production possibility and easy shaping of elements of glasses, oxyfluoride glass and glass-ceramics may combine the particular optical properties of rare-earth ions in nano-crystalline fluoride host with the chemical stability and mechanical property of oxide glasses [1]. The Tb-doped lithiumlanthanum-aluminosilicate glass was previously reported to have large rare-earth solubility and a good luminescence light-yield [1]. The visible to near-infrared quantum cutting (QC) was reported for Tb and Yb co-doped YbxY1-xPO4:Tb3+ powder and polyborates [2, 3]. The search for QC phosphors converting light from vacuum ultraviolet to visible provided special interest because of potential applications in plasma display and mercury-free lighting while the QC phosphors converting light from visible to near-infrared may have its potential application in silicon-based solar cells [2-5]. The transparent oxyfluoride glass-ceramic containing fluoride nanoparticles (NPs) in rare-earth doped glasses may enhance the luminescence of rare-earth ions [1, 6-8]. The increased luminescence yield was attributed to the low phonon energy of the heavy-metal fluoride [6-8]. The QC process in Tb and Yb co-doped materials is based on the energy transfer from excited Tb3+ ions to Yb3+ ions. The energy transfer efficiency is expected to increase with a decrease in the distance between Tb3+ and Yb3+ ions. In oxyfluoride glass-ceramics containing LaF3 nanocrystals, a significant number of
Data Loading...
