Excited-state dynamics and optical bistability in the dimer system Cs3Lu2Br9:Yb3+

Cooperative visible upconversion is reported in crystals of Cs3Lu2Br9:1% Yb3+, Cs3Lu2Br9:10% Yb3+, and Cs3Yb2Br9. The near-infrared emission decays twice as fast as the visible emission as expected from theory. Both, the 10% and the 100% crystals exhibit bistability of the luminescence intensity as a function of the excitation intensity at temperatures below 30 K. The bistable region gets narrower and moves to lower excitation intensities with increasing temperature and concentration. Both trends are in accordance with theoretical models. (C) 1998 Published by Elsevier Science B.V. All rights reserved.