Abstract
Y2O3 codoped with Bi3+ and Yb3+ is considered as an efficient downconversion material combining strong broadband absorption of Bi3+ with photon splitting by cooperative energy transfer from Bi3+ to two Yb3+ neighbors. However, evidence for photon splitting is lacking. Here we investigate the Bi3+-to-Yb3+ energy-transfer mechanism. For cooperative energy transfer the Yb3+-concentration-dependent luminescence decay will show clear characteristics of cooperative dipole-dipole transfer. Analysis of Yb3+-concentration and temperature-dependent decay curves however demonstrates that the energy-transfer mechanism is not cooperative but single step, probably through a Bi4+-Yb2+ charge-transfer state. The temperature dependence of the Bi3+-to-Yb3+ energy-transfer efficiency is unusual as it decreases with temperature, unlike commonly observed thermally activated energy transfer. This is a signature of energy transfer via exchange interaction. The present results provide evidence for the absence of photon splitting in Y2O3:Bi3+,Yb3+ and form a convincing demonstration of exchange interaction mediated energy transfer.
Original language | English |
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Article number | 134308 |
Journal | Physical Review B |
Volume | 98 |
Issue number | 13 |
DOIs | |
Publication status | Published - 17 Oct 2018 |
Funding
Financial support from National Science Foundation of China (Grants No. U1601205, No. 51472088, and No. 51125005) is gratefully acknowledged. T.Y. would like to thank China Scholarship Council (CSC, File No. 201606150005) for scholarship support.