BaMgAl10Ol7：Eu^2＋,Yb^3＋ was investigated as a possible quantum cutting system to enhance solar cells efficiency. Phosphors were synthesized by combustion method and composed of nanorods. Photoluminescence spectra showed that Eu in the sample was reduced to bivalence while Yb remained trivalence. Through a cooperative energy transfer process, the obtained powders exhibited both blue emission of Eu^2＋ （around 450 nm） and near infrared emission of Yb^3＋ （around 1020 nm） under broad band excitation （250-410 nm） originating from 4f→5d transition of Eu2＋. Energy transfer phenomenon between the sensitizer Eu2＋ and the activator Yb3＋ was investigated via the luminescent spectra and the decay curves of Eu2＋ with different Yb3＋ concentrations. Results indicated that energy transfer efficiency from Eu2＋ to Yb3＋ was not high. The poor efficiency can be explained by the long distance between rare earth ions.
The 4f-5d transitions of Er3+ ions doped in crystals were widely studi ed due to their potential applications in quantum cutting phosphors and VUV lase rs,etc.The theory to do the calculations of 4f-5d transitions and various rela ted aspects,such as the ways to determining various parameters,were summarized .The impacts of various interactions on the spectra were also demonstrated clea rly with Er3+ ions in crystals CaF2 and LiYF4.Predicted results were compared w ith measured spectra.
The local coordination structures around the doping Yb2＋ ions in sodium and potassium halides were calculated by using the first-principles supercell model. Both the cases with and without the charge compensation vacancy in the local environment of the doping Yb2＋ were calculated to study the effect of the doping on the local coordination structures of Yb2＋. Using the calculated local structures, we obtained the crystal-field parameters for the Yb2＋ ions doped in sodium and potassium halides by a method based on the combination of the quantum-chemical calculations and the effective Hamiltonian method. The calculated crystal-field parameters were analyzed and compared with the fitted results.
We constructed an effective one-electron Hamiltonian by using the 4f/5d energies and eigenvectors obtained from the first-principles calculation with the relativistic self-consistent discrete variational Slater software package （DV-Xα）. From the effective Hamiltonian, we obtained the crystal-field and spin-orbit interaction parameters for the 4f and 5d electrons of lanthanide ions （Ce^3＋, Pr^3＋, Nd^3＋ and Eu^3＋） doped in YPO4, and these parameters were used to calculate the 4fN-4fN- 15d transition. Comparison with experiments shows that the obtained parameters are reasonable and the excitation spectra can be well predicted.
