Optical absorption of Ni²⁺ and Ni³⁺ ions in gadolinium gallium garnet epitaxial films

Abstract

Single-crystal Ni-doped gadolinium gallium garnet films were grown for the first time from supercooled Bi2O3–B2O3-based melt solutions by liquid-phase epitaxy. Optical absorption bands due to Ni2+, Ni3+ and Bi3+ ions were observed in those films. Interpretation and tabulation of all absorption bands of nickel ions occupying octahedral and tetrahedral sites in the garnet lattice are presented.

Broadband-sensitive Ni2+–Er3+ based upconverters for crystalline silicon solar cells

“…For the Ni only doped (no Er) sample, broad emission band ranging from 1300 nm to 1600 nm originated from the 3 T 2 ( 3 F) / 3 A 2 ( 3 F) transition of Ni 2+ was observed. [26][27][28][29][30][31][32][33] However, by introducing Er 3+ (Li + ) co-dopants, the Ni 2+ emission almost disappeared and Er 3+ emissions at around 1550 nm ( 4 I 13/2 / 4 I 15/2 ) and 980 nm ( 4 I 11/2 / 4 I 15/2 ) appeared (see Fig. S5 † for 1180 nm excited UC at 980 nm).…”

“…[24][25][26][27][28][29][30][31] It has been demonstrated that six coordinated Ni 2+ ions located at the centers of octahedrons have substantial absorption around 1100-1400 nm that can further be tuned in a wide range by manipulating the crystal eld strength around the Ni 2+ ions. 26,30,32 Accordingly, its NIR emission band is also wide ranging from 1200 nm to longer than 1700 nm with extremely high quantum yield reaching unity in some crystals such as LiGa 5 O 8 .…”

“…[24][25][26][27][28][29][30][31] It has been demonstrated that six coordinated Ni 2+ ions located at the centers of octahedrons have substantial absorption around 1100-1400 nm that can further be tuned in a wide range by manipulating the crystal eld strength around the Ni 2+ ions. 26,30,32 Accordingly, its NIR emission band is also wide ranging from 1200 nm to longer than 1700 nm with extremely high quantum yield reaching unity in some crystals such as LiGa 5 O 8 . 33 There are other reports of the Ni 2+ emission bands in the NIR ranges [25][26][27][34][35][36][37] that sufficiently overlap with the Er 3+ absorption bands making possibility of Ni 2+ / Er 3+ resonance energy transfer (sensitization).…”

“…26,30,32 Accordingly, its NIR emission band is also wide ranging from 1200 nm to longer than 1700 nm with extremely high quantum yield reaching unity in some crystals such as LiGa 5 O 8 . 33 There are other reports of the Ni 2+ emission bands in the NIR ranges [25][26][27][34][35][36][37] that sufficiently overlap with the Er 3+ absorption bands making possibility of Ni 2+ / Er 3+ resonance energy transfer (sensitization). 32,38,39 Zhang et al has reported that Ni 2+ to Er 3+ energy transfer or vice versa in glass ceramics depending on the host matrix and Ni 2+ to Er 3+ physical separation to achieve NIR broadband Stokes emission for amplier and lasers.…”

“…34 Thus, the host materials to realize broadband-sensitive upconversion using Er 3+ and Ni 2+ dopants are selected according to the following three criteria: (1) the host material must include cations located at octahedron centers, and should not include tetrahedron or other symmetry sites that can be occupied by Ni 2+ ions. Four co-ordinated Ni 2+ ions located at tetrahedron centers and Ni 3+ have lower energy levels 26,30 and hence rapid relaxation occur rather than energy transfer to the Er 3+ emitters aer photoexcitation. (2) The ionic radius of the cations located at the octahedron centers should be close to or at least not much smaller than that of Ni 2+ (0.069 nm) to enable a high Ni 2+ concentration, otherwise introduced Ni 2+ ions would change to smaller Ni 3+ ions (0.056 nm) or segregate.…”