Upconversion properties in lanthanide doped layered-perovskite, CsBiNbO.

Despite advances of lanthanide-doped upconversion (UC) materials, the applications such as light-emitting diode and biological imaging are limited by low quantum efficiency. For this context, the understanding of unique interactions between the doped-lanthanides and the host crystals has attracted a huge amount of the researcher's interest. In particular, it was revealed that doping lanthanide ions in a non-centrosymmetric site of host lattice is the cause of relaxation of the Laporte selection rule in the 4f-4f transition of lanthanide ions. One of the layered perovskites CsBiNbO is known to have non-centrosymmetric sites, which would lead to highly bright UC emission. Nevertheless, to our knowledge, there has been no research on the UC comparison between host materials of CsBiNbO with other hosts. In this article, we present the UC intensity comparison of Yb-Er ion doped CsBiNbO, NaYF, BaTiO, and SrTiO hosts (the UC in CsBiNbO:Er,Yb was 2.4 times that of NaYF:Er,Yb and ∼70 times that of SrTiO:Er,Yb). After that, we dig into UC, downshifting, and double beam system UC properties. The activator concentration was optimized by varying the doping ratio of Yb and Er, and we found out the main reason for the concentration quenching behavior in Er ion doped CsBiNbO is dipole-dipole interaction. In addition, the double excitation experiment indicates that the absorption (I → I) factor is stronger than the stimulated emission (I → I) factor in CsBiNbO under 1540 nm laser irradiation.