Yb3+-sensitized visible Ni2+ photon upconversion in codoped CsCdBr3 and CsMgBr3 -: art. no. 125111

Near-infrared excitation of Yb3+ F-2(7/2)->F-2(5/2) at 10 600 cm(-1) in the linear chain CsMBr3:Ni2+,Yb3+ (M=Cd,Mg) structure leads to green luminescence from Yb3+ pairs and red Ni2+ upconversion luminescence at cryogenic temperatures. The broad red upconversion luminescence is assigned to the T-1(2g)->(3)A(2g) transition of Ni2+. The upconversion excitation spectrum indicates that the active mechanism in these systems involves both Yb3+ and Ni2+ ions. Lifetime and power dependence data allow one to identify a ground-state-absorption (GSA) energy-transfer upconversion (ETU) as the underlying upconversion mechanism for the Yb3+-Ni2+ system in doubly doped CsCdBr3 and CsMgBr3. A less efficient single-ion GSA excited-state-absorption (ESA) process within Ni2+ is also observed in the title compounds. However, whereas the GSA/ESA process requires an excitation energy above 11 200 cm(-1), it is possible to sensitize the Ni2+ upconversion via Yb3+ excitation at energies around 10 200 cm(-1) and around 10 600 cm(-1) in CsCdBr3 and CsMgBr3. It is shown that only those Ni2+ ions neighboring to Yb3+ ions are relevant for the upconversion induced by Yb3+ excitation.