Upconversion luminescence of Er3+, Tm3+ and Yb3+Co-doped Gd3Ga5O12 nanocrystals

Deep red upconversion photoluminescence in Er3+‐doped Yb3Ga5O12 nanocrystalline garnet

“…However, it should be noted that, even in the highly Er 3+ ‐doped samples, the green and red UCPL emission intensities do not differ so significantly as in the Er 3+ and heavily Yb 3+ ‐co‐doped samples 33,34 . For example, the green UCPL emission dominates over the red UCPL emission in the 1 at.% Er 3+ ‐doped Gd 3 Ga 5 O 12 garnet 27 or 1 at.% Er 3+ ‐doped nanocrystalline ZrO 2 31 at the pumping wavelength of ≈980 nm. However, the addition of Yb 3+ ions into the mentioned hosts changes the dominance of the green UCPL emission to the red UCPL by orders of magnitude, and in some cases, the green UCPL emission is almost quenched 31,34,35,52,54 .…”

“…It should be noted that the phonon‐assisted processes depend on the phonon energy of a host matrix 34,35 as well as on the content of the impurities such –OH groups 57,58 . However, in many lightly Er 3+ ‐doped bulk and nanocrystalline hosts, such as Gd 3 Ga 5 O 12 , 27 Ge 25 Ga 8 As 2 S 65 , 55 ZrO 2 , 59 Lu 2 O 3 , 60 BaTiO 3 , 61 Na 0.5 Bi 0.5 TiO 3 , 62 Ba 3 Lu 4 O 9 , 63 GdOCl, 64 NaYF 4 65 or RbGd 2 Cl 7 , and RbGd 2 Br 7 , 66 the green UCPL emission dominates over the red UCPL. Compared to that, the increase of the Er 3+ ion concentration in a solid shortens the interatomic distance between the adjacent Er 3+ ions, and it results in the decrease of the green‐to‐red UCPL emission intensity ratio 49–56 .…”

“…27 The introduction of Yb 3+ ions improves the overall UCPL efficiency due to the sensitized energy transfer upconversion (ETU) and promotes the red Er 3+ : 4 F 9/2 → 4 I 15/2 UCPL emission over the green Er 3+ : 4 F 7/2 / 2 H 11/2 / 4 S 3/2 → 4 I 15/2 UCPL. [25][26][27] Moreover, the Yb 3+ : 2 F 7/2 → 2 F 5/2 absorption cross-section is notably larger, but in resonance to Er 3+ : 4 I 15/2 → 4 I 11/2 absorption cross-section, thus allowing the efficient excitation with ≈980 nm laser light. Therefore, the way to achieve the intense Er 3+ UCPL emission may be seen in using of the Yb-based garnet host where the Yb 3+ ions may be substituted with Er 3+ .…”

“…26 These types of singly Er 3+ -doped garnets exhibit the intense green Er 3+ : 4 F 7/2 / 2 H 11/2 / 4 S 3/2 → 4 I 15/2 UCPL emission at a pumping wavelength of ≈980 nm. 27 The introduction of Yb 3+ ions improves the overall UCPL efficiency due to the sensitized energy transfer upconversion (ETU) and promotes the red Er 3+ : 4 F 9/2 → 4 I 15/2 UCPL emission over the green Er 3+ : 4 F 7/2 / 2 H 11/2 / 4 S 3/2 → 4 I 15/2 UCPL. [25][26][27] Moreover, the Yb 3+ : 2 F 7/2 → 2 F 5/2 absorption cross-section is notably larger, but in resonance to Er 3+ : 4 I 15/2 → 4 I 11/2 absorption cross-section, thus allowing the efficient excitation with ≈980 nm laser light.…”

“…The UCPL emission from Er 3+ ‐doped and/or Er 3+ /Yb 3+ ‐co‐doped garnet hosts has been studied for example in Y 3 Al 5 O 12 25 and Gd 3 Al 5 O 12 26 . These types of singly Er 3+ ‐doped garnets exhibit the intense green Er 3+ : 4 F 7/2 / 2 H 11/2 / 4 S 3/2 → 4 I 15/2 UCPL emission at a pumping wavelength of ≈980 nm 27 . The introduction of Yb 3+ ions improves the overall UCPL efficiency due to the sensitized energy transfer upconversion (ETU) and promotes the red Er 3+ : 4 F 9/2 → 4 I 15/2 UCPL emission over the green Er 3+ : 4 F 7/2 / 2 H 11/2 / 4 S 3/2 → 4 I 15/2 UCPL 25–27 .…”