Thermally deactivated energy transfer in Bi3+−Yb3+

Abstract

Y 2 O 3 codoped with Bi 3+ and Yb 3+ is considered as an efficient downconversion material combining strong broadband absorption of Bi 3+ with photon splitting by cooperative energy transfer from Bi 3+ to two Yb 3+ neighbors. However, evidence for photon splitting is lacking. Here we investigate the Bi 3+-to-Yb 3+ energy-transfer mechanism. For cooperative energy transfer the Yb 3+-concentration-dependent luminescence decay will show clear characteristics of cooperative dipole-dipole transfer. Analysis of Yb 3+-concentration and temperature-dependent decay curves however demonstrates that the energy-transfer mechanism is not cooperative but single step, probably through a Bi 4+-Yb 2+ charge-transfer state. The temperature dependence of the Bi 3+-to-Yb 3+ 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 Y 2 O 3 : Bi 3+ , Yb 3+ and form a convincing demonstration of exchange interaction mediated energy transfer.

Recent advances and prospects of persistent luminescent materials as inner secondary self-luminous light source for photocatalytic applications

“…This, as we will discuss further, is of particular interest and importance for the MPL@PCM composites design. In addition, the up-converting optical properties of the RE ions like the Yb 3+ [183,302], Er 3+ /Yb 3+ [303], and Er 3+ /Tm 3+ /Yb 3+ [304] can sometimes be modified by Bi 3+ ion. Although the number and type of Bi 3+ MPLs are also not plentiful as compared to those RE-based MPLs, they are desirable for the photocatalytic purposes due to the broad and host-dependent persistent range (Figure 8).…”

“…These compounds are referred to the up-converted MPLs (UC-MPLs), and they are mostly activated with the 808 nm and 980 nm NIR light. In this case, to realize the UC process in UC-MPLs, it generally needs an Yb 3+ ion that efficiently absorbs the 980 nm NIR photons or an Nd 3+ ion that can absorb the 808 nm NIR photons [40,135,143,193,[302][303][304][343][344][345][346][347][348][349][350][351][352][353][354][355][356][357][358][359].…”

Recent Advances in Luminescent Downconversion: New Materials, Techniques, and Applications in Solar Cells

“…Besides, breakthrough of NIR‐DC was achieved in Er 3+ and/or Ho 3+ singly doping, where an incident UV/green photon is split into two or more photons re‐emitted at ≈1530 and 1200 nm, respectively. [ 39a–c,40,71 ] Such kind of efficient NIR splitters well meet the requirement of narrow‐bandgap solar cells like CuInSe 2 , GaSb, and Ge, IR lasing, optical communication, etc. Till now, a series of multi‐photon splitting were reported in Dy 3+ , Tm 3+ , Pr 3+ , and Nd 3+ singly doping, [ 39d–j,72 ] where a maximum QY was evaluated to be greater than 300%.…”

“…Yu et al further reviewed the dependence of MR rate (W NR ) on energy gap for Ln 3+ ions in various hosts Figure 7c, and found that only in hosts with low phonon energies, such as fluorides, chlorides, and bromides, W NR of the 4 I 9/2 excited state would be equal to or slower than the radiative transition rates (W R ). [40] Besides, dependence of W NR /W R ratio of Er 3+ 4 I 9/2 level on phonon energy in some classical hosts Figure 7d indicates that hosts with phonon energy < 350-450 cm -1 and/or with special luminescence environment would endow long-lived Er 3+ 4 I 9/2 state for effective three-photon cutting in Er 3+ -doping systems. [76] and c) NIR regions to distinguish the photon-splitting process; Reproduced with permission.…”

“…[ 39 ] Compared with Ln 3+ /Yb 3+ co‐doping, the single doping system features a broaden absorption spanning UV‐NIR region, and meanwhile extends the “split” photon re‐emissions in a tunable region of ≈800–2000 nm. By rational calculations, optimal internal QYs greater than unity were obtained for the two‐ or three‐photon splitting systems, such as Pr 3+ splitter for one blue photon‐to‐two NIR ≈ 1000 nm photons, [ 39i ] Er 3+ splitter for one green photon‐to‐two NIR ≈ 1530 nm photons, [ 39a,40 ] etc. and that more than 2 were achieved for the three‐ or four‐photon cutting systems, such as Er 3+ splitter for one UV photon‐to‐four NIR ≈ 1530 nm photons, [ 39b ] Tm 3+ splitter for one UV photon‐to‐four NIR ≈ 1850 nm photons, [ 39f–h ] etc.…”