Enhancement of emission intensity of LaVO4:RE3+ luminescent solar light absorbers

The investigated La1-xRExVO4 (RE = Eu, Sm) solid solutions are characterized by intensive emission of the RE ions that is excited from the wide spectral range including UV region of intrinsic transitions in the vanadate host. We have carried out comparable analysis of characteristics of the La1-xRExVO4 compounds synthesized by three different methods: solid state reaction, co-precipitation and sol-gel synthesis. The investigation revealed differences in luminescence and excitation spectra of samples obtained by different methods. Spectra of the samples with lower activator concentrations have a more complicated character. They contain exceed number of lines that is caused by formation of two types of RE3+ emission centers. Spectral exhibitions of the second ("at surface") type of centers are observed up to x = 0.05, 0.1 and 0.3 for samples synthesized by solid state, co-precipitation and sol-gel methods, respectively. The presence of the "at surface" type of centers leads to essential increasing of total intensity of emission. Differences in excitation spectra give us a possibility to suppose that enhancement of luminescence intensity is also due to expanded excitation range caused by "at surface" centers in UV region. Therefore, "at surface" centers satisfy better absorption of UV light. (C) 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim