Relaxation of the 4fn-15d1 electronic states of rare earth ions in YPO4 and YBO3

Large band-gap materials doped with rare earth-ions are currently of great interest as new vacuum UV phosphors for lighting and displays. In this report, the optical properties of YPO4 and YBO3 doped with Pr, Tm, Er, and Eu are described. The emission resulting from the VUV excitation of the parity allowed 4fn-15d1 states and their quantum efficiencies are reported. Relaxation between the 4fn-15d1 and nearby 4fn excited states is observed for some of these ions, and the dynamics of these excited states is reported. In doubly-doped samples, the prospects for quantum cutting by using cross relaxation energy transfer in which some of the energy of the initially excited 4fn-15d1 state is transferred to an acceptor ion so that both donor and acceptor ions are left in an excited state from which they each can emit a photon are examined. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)