Origin of visible and near IR upconversion in Yb3+-Tm3+-Er3+ doped BaMgF4 phosphor through energy transfer and cross-relaxation processes

Abstract

Near infrared and green, red emission through upconversion and energy transfer processes in BaMgF 4 doped with Yb 3þ-Tm 3þ and Yb 3þ-Tm 3þ-Er 3þ excited at 980 nm were investigated. The BaMgF 4 :Yb 3þ ,Tm 3þ phosphor showed a dominating UC emission at 800 nm. The origin of this 800 nm emission peak was explored through different possible cross-relaxation processes. The optimized composition of Yb 3þ and Tm 3þ was further co-doped with Er 3þ , these compositions also showed dominating 800 nm emission for lower concentrations of Er 3þ which was gradually suppressed at higher Er 3þ concentration. The enhancement of the visible emission of Er 3þ in the BaMgF 4 :Yb 3þ ,Tm 3þ ,xEr 3þ doped phosphor suggests the efficient energy transfer from Yb 3þ to Tm 3þ and Tm 3þ to Er 3þ. By tuning the concentrations of the dopants, a near white light emission under infrared excitation was also achieved.

Tailoring of Upconversion Emission in Tm3+/Yb3+-Codoped Y2Mo3O12 Submicron Particles Via Thermal Stimulation Engineering for Non-invasive Thermometry

“…Notably, the lattice contraction can not only decrease the distance between Yb 3+ and Tm 3+ but also it is able to shorten the distance of adjacent Tm 3+ . As proposed, , the cross-relaxation (CR) process can happen in Tm 3+ -doped luminescent materials, and its rate will be enhanced when the distance between Tm 3+ declines. In particular, there are mainly three CR processes, namely, 3 H 4 + 1 G 4 → 1 D 2 + 3 F 4 , 3 H 4 + 1 G 4 → 3 F 4 + 1 D 2 , and 3 H 6 + 1 G 4 → 3 F 4 + 3 F 2,3 , in the Tm 3+ -doped luminescent materials, as illustrated in Figure c.…”

Achieving high-sensitivity dual-mode optical thermometry via phonon-assisted cross-relaxation in a double-perovskite structured up-conversion phosphor

“…The emission intensities of 475, 649 and 694 nm are mostly determined by the collaborative action of two non-radiative transitions (NR1: 3 H 5 → 3 F 4 and NR2: 3 H 5 → 3 F 4 ) and three cross-relaxation processes (CR1: 3 H 4 + 1 G 4 → 1 D 2 + 3 F 4 , CR2: 3 H 4 + 1 G 4 → 3 F 4 + 1 D 2 , CR3: 3 H 6 + 1 G 4 → 3 F 4 + 3 F 2,3 ). 45,52–54 However, it should be noted that the occurrence probability of these two non-radiative transition processes and three cross relaxation processes highly depends on the phonon energy of the matrix crystal. At room temperature, the UC luminescence is mainly affected by multi-phonon-assisted non-radiative transition processes of NR1 and NR2, while the cross-relaxation process probably has little effect on the up-conversion luminescence process.…”

“…The origin of the high-sensitivity optical thermometry of ALaLiTeO 6 :5%Yb 3+ ,0.2%Tm 3+ is related to the significant difference in the response of the transition emission intensity of the three-photon process and the two-photon process to temperature changes. The emission intensities of 475, 649 and 694 nm are mostly determined by the collaborative action of two non-radiative transitions (NR1: 3 H 5 → 3 F 4 and NR2: 3 H 5 → 3 F 4 ) and three cross-relaxation processes (CR1: 3 45,[52][53][54] However, it should be noted that the occurrence probability of these two non-radiative transition processes and three cross relaxation processes highly depends on the phonon energy of the matrix crystal. At room temperature, the UC luminescence is mainly affected by multi-phonon-assisted non-radiative transition processes of NR1 and NR2, while the cross-relaxation process probably has little effect on the upconversion luminescence process.…”

Thermochromic Upconversion Emission in Tm3+/Yb3+-Codoped La2Mo3O12 Microparticles via Negative Thermal Expansion Engineering for Ultrahigh Sensitivity Optical Thermometry

“…It is clear that the cross-relaxation (CR) process exists in Tm 3+ -based luminescent compounds, where the possibility of the CR process is highly related to the space of adjacent Tm 3+ , that is, small distance results in a strong CR process. 44,48 In terms of the CR process of Tm 3+ , it usually involves three different parts, namely, 3…”

“…Furthermore, the temperature-induced lattice shrinkage can not only shorten the distance between Tm 3+ and Yb 3+ but also decrease the distance of nearby Tm 3+ . It is clear that the cross-relaxation (CR) process exists in Tm 3+ -based luminescent compounds, where the possibility of the CR process is highly related to the space of adjacent Tm 3+ , that is, small distance results in a strong CR process. , In terms of the CR process of Tm 3+ , it usually involves three different parts, namely, 3 H 4 + 1 G 4 → 1 D 2 + 3 F 4 (CR1), 3 H 4 + 1 G 4 → 3 F 4 + 1 D 2 (CR2), and 3 H 6 + 1 G 4 → 3 F 4 + 3 F 2,3 (CR3), as described in Figure S8. Obviously, these CR processes have the capacity of contributing to the depopulation of the 1 G 4 level, and the population of 3 F 4 and 3 F 2,3 levels will be promoted via these CR processes.…”