White upconversion emission in CaHfO3 with codoping of Er3+, Ho3+, and Tm3+

Abstract

We investigated the upconversion luminescence (UCL) properties of CaHfO3 co-doped with Er3+, Ho3+, Tm3+, and Yb3+ to realize white UCL. We first verified that the UCL spectra of Tm3+/Yb3+ co-doped CaHfO3 (Yb3+ functioning as a sensitizer) showed a weak blue emission at 470 nm. It was assigned to the transition (1)G(4) -> H-3(6) that occurs via three photon absorption. We combined the blue UCL in Tm3+ with the green and red UCL in Er3+ and Ho3+ in a triply doped CaHfO3. It was observed that the blue UCL of Tm3+ was rather weak to generate a white UCL with the aid of Er3+ and Ho3+. In addition, double-doping with Tm3+ and Ho3+ was optimal for white UCL in CaHfO3. We examined the UCL properties of Tm3+/Ho3+ co-doped CaHfO3 in terms of their dependence on temperature and the concentration of Tm3+. We also discussed the feasibility of realizing white UCL in CaHfO3.