Energy transfer in Tb3+- Yb3+ doubly doped CsGd(MoO4)2 single crystals for contactless thermometry, solid-state lighting and solar cells

A novel terbium (Tb3+) and ytterbium (Yb3+) co-doped optical quality CsGd(MoO4)2 single crystals were grown by the low-thermal-gradient Czochralski method. Photoluminescence spectra were measured and studied for Tb3+– Yb3+ doubly doped CsGd(MoO4)2 crystals at 77–340 K temperature range. Under 330 nm excitation the main peaks of Tb3+ and Yb3+ emission were observed. Decay curves were obtained for the energy levels 5D4 of Tb3+ and 2F7/2 of Yb3+ in CsGd(MoO4)2 crystals. Decay time for Tb3+ transitions significantly varies at temperatures close to ambient. Such behaviour allows to assume perspective application of this effect for non-contact luminescence lifetime thermometry. The emission colour chromaticity coordinates of CsGd(MoO4)2: Tb3+ -Yb3+ crystals are close to SMPTE (Society of Motion Picture and Television Engineers) standard for green colour, as shown on CIE 1931 diagram. Correlated colour temperature varies from 5538 K at 77 K to 4297 K at 340 K.