Xiumei Yin

Upconversion luminescence of Y2Ti2O7:Er3+ under 1550 and 980 nm excitation

Abstract Er 3+ doped Y 2 Ti 2 O 7 phosphors were prepared by the high temperature solid state reaction method at 1500 °C. X-ray diffraction and luminescence spectra were used to characterize the properties of samples. Due to the layer distribution of Y 3+ ions in the pyrochlore Y 2 Ti 2 O 7 crystal, Er 3+ ions, replacing Y 3+ in Y 2 Ti 2 O 7 crystal, could realize high-concentration doping by suppressing energy migration between layers to minimize concentration quenching. Investigation on the upconversion characteristic of Y 2 Ti 2 O 7 :Er 3+ showed that the optimal doping concentration of Er 3+ was up to 28 mol.%. Y 2 Ti 2 O 7 :0.28 Er 3+ exhibited both dominating red emission under 980 and 1550 nm excitation. The brightness of Y 2 Ti 2 O 7 :0.28Er 3+ were 4 times (980 nm) and 7 times (1550 nm) higher than that of Y 2 Ti 2 O 7 :0.05Er 3+ . And Y 2 Ti 2 O 7 :Er 3+ presented much better red emission color purity and stability under 1550 nm excitation.

Simple method for simultaneously achieving red and green up-conversion luminescence

The simultaneous emission of red and green light with high brightness and color purity was obtained from Er3+-doped NaYbF4-based up-conversion nanoparticles excited by 980 and 1550 nm excitation. The 2F5/2 level of Yb3+ showed high absorption efficiency at 980 nm. The 4I13/2 level of Er3+, an excellent UC intermediate with high energy and a long lifetime (milliseconds), absorbed more energy in the cross section (6.0 × 10−20 cm2) than did the Yb3+ 2F5/2 level (1.2 × 10−20 cm2) and was efficiently and directly pumped by light with a wavelength of ∼1500 nm. In contrast to particles resulting from other methods using complex coating for achieving multi-color emission in a single sample, the as-prepared luminescent NaYbF4:25% Er3+ up-conversion nanoparticles were designed to be single-layered and spherical and showed excellent dispersibility and uniform sizes. Nanoparticles prepared by this method exhibit a great advantage based on the simple preparation process and small particle size. On this basis, we expect to easily achieve the emission of three primary colors by these reasonably designed core–shell particles.

K3LaTe2O9:Er: a novel green up-conversion luminescence material

A novel green up-conversion luminescence material, K3LaTe2O9:Er, was synthesised via a solid-state reaction method. K3LaTe2O9:Er phosphors were characterised by X-ray diffraction, reflectance spectroscopy, Raman spectroscopy, photoluminescence spectroscopy, up-conversion spectroscopy and temperature sensing performance analysis. The diffraction pattern of the hexagonal K3LaTe2O9:0.02Er microcrystals was indexed with Miller indices and the lattice constants were a = b = 0.60636 ± 0.00018 nm, and c = 1.49543 ± 0.00037 nm. The photoluminescence under 380 nm excitation and the up-conversion luminescence under 980 and 1550 nm pumping were investigated. The influence of Er3+ ion concentration and excitation power on the luminescence properties of K3LaTe2O9:Er was also discussed. K3LaTe2O9:Er phosphor presented green down-shifting emission and up-conversion luminescence under 380, and 980 nm excitation and yellow–green up-conversion luminescence under 1550 nm pumping, respectively, and the red emission component was enhanced with the increment in excitation wavelength. The quenching concentration of Er3+ ions in K3LaTe2O9:Er was much higher than that in normal phosphors. This result can be attributed to the suppression of energy migration because the shortest (0.606 nm) and average distance (0.9720 nm) between Er3+ ions were significantly large in K3LaTe2O9. Therefore, the electric quadrupole–quadrupole interactions between Er3+ ions are the dominant energy transfer process in down-shift emission, and the UCL mechanism can be regarded as the excited state absorption in K3LaTe2O9:Er. Furthermore, the doping concentration of Er3+ ions influenced the temperature sensitivity of K3LaTe2O9:Er.

Up-conversion luminescence of Er2Mo4O15 under 980 and 1550 nm excitation

Y2−xErxMo4O15 (x = 0.04, 0.08, 0.16, 0.32, 0.64, 2.0) phosphors were synthesised at 700 °C through a solid-state reaction method. The samples were characterised by XRD and emission spectra analysis. Y2−xErxMo4O15 samples showed a strong green emission (2H11/2, 4S3/2 → 4I15/2) and a weak red emission (4F9/2 → 4I15/2) under 1550 and 980 nm excitation. The green emission intensity was enhanced increasing the Er3+ ion doping content, whereas the red emission was basically unchanged. Thus, Er2Mo4O15 exhibited an abnormal green up-conversion luminescence without concentration quenching under 1550 and 980 nm excitation. The dominating green up-conversion luminescence was due to the larger adjacent Er3+⋯Er3+ distance caused by the special structure of Er2Mo4O15, which limited the energy-transfer process and cross-relaxation responsible for the red up-conversion emission. Therefore, the up-conversion luminescence mechanism was excited-state absorption under 1550 nm excitation.

Luminescence property tuning of Yb3+-Er3+ doped oxysulfide using multiple-band co-excitation

Lanthanide ions have abundant excited-state channels which result in a radiation relaxation process generally accompanied by a non-radiation relaxation process. However, non-radiation relaxation processes will consume the activation energy and reduce the luminescence efficiency of the phosphor. Two lasers with an excitation energy which matched the ground state absorption and excited state absorption of ions were used to excite the phosphors to avoid the non-radiation relaxation process. This approach can achieve the purpose of populating specific states of the lanthanide ions, and furthermore effectively tunes the luminescence intensity and color output of the sample. Results show that the red emission intensity of the sample is significantly improved and this is caused by populating the 4F9/2 level under simultaneous 1510 nm and 980 nm excitation. Then when the 1510 nm and 808 nm co-operate to excite the sample, the green emission obtained increased sharply because the 2H11/2/4S3/2 states were efficiently populated. As a proof-of-concept experiment, this new approach has potential in the applications of solar cells.

Correction: Luminescence property tuning of Yb3+–Er3+ doped oxysulfide using multiple-band co-excitation

Correction for ‘Luminescence property tuning of Yb3+–Er3+ doped oxysulfide using multiple-band co-excitation’ by Hong Wanga et al., RSC Adv., 2018, 8, 16557–16565.