Terbium Ion-Mediated Energy Transfer in WO₃:Tb³⁺ and Eu³⁺ Phosphors for UV-Sensitized White Light Emission

Abstract

Incorporation of suitable lanthanide (Ln 3+ ) ions into semiconducting WO 3 can be useful to produce host-sensitized luminescence for solid-state lighting applications. Codoping of another Ln 3+ ion can assist in transferring energy from the host to the activator Ln 3+ ion to produce bright luminescence depending upon the electronic structure of the doped system. As a case study, Eu 3+ and Tb 3+ ion−doped WO 3 phosphors (WO 3 :Tb 3+x Eu 3+ y , x = 0−0.05 and y = 0−0.20) have been prepared over a wide range of doping concentrations to investigate the role of the Tb 3+ ion as a sensitizer and realize host-sensitized emission from Eu 3+ ions. The steady-state and time-resolved photoluminescence (TRPL) data for WO 3 :Tb 3+x Eu 3+ y (x = 0−0.05 and y = 0−0.10) samples confirm that Tb 3+ ions assist in excitation of Eu 3+ ions via sequential energy transfers from the host to Tb 3+ ions followed by Tb 3+ to Eu 3+ ions. The energy transfer process is controlled by optimizing their doping concentrations, and a single-phase white-light-emitting phosphor with a composition WO 3 :Tb 3+ 0.05 Eu 3+ 0.0005 has been developed. The electronic band structures and projected density of state plots for the WO 3 :Tb 3+ 0.03125 Eu 3+ 00.03125 system obtained using density functional theory (DFT)-based simulations confirm the formation of impurity states due to Eu 3+ and Tb 3+ ions within the forbidden gap of WO 3 . Based on the TRPL and DFT data, it is confirmed that the Tb 3+ ions act as a bridge between the conduction band edge of WO 3 and excited states of Eu 3+ ions to transfer energy and facilitate characteristic emission from europium species.

Evaluating Inter-Lanthanide Interactions in Co-Doped Zinc Sulfide Nanoparticles for Multiplex Assays

“…Several researchers reported multiple Ln-containing assemblies in order to address their use as multiplex assays. These include metal–organic frameworks and NP − systems. Inclusion of co-dopants into an NP allows the possibility of “cross talk” between the luminophores and their sensitization.…”

“…50 These authors argued that the second Ln 3+ can introduce additional nonradiative decay pathway(s) and modulate the local environment of the initial dopant, thereby opening the possibility of emission quenching and enhancement, respectively. Sivakumar and co-workers 51 discussed generation of white light from Tb and Eu co-doped WO 3 NPs and how an optimum emission output can be generated by manipulating the relative dopant concentrations. The use of Ln-containing NPs for multiplex assays is reviewed by Liu and co-workers.…”

Maximizing Terbium–Europium Electronic Interaction: Insight from Variation of Excitation Energy

“…Another fascinating avenue is to dope multiple and distinct Ln 3+ in an NP to generate co-doped NPs. − These assemblies are particularly attractive to access luminophores for multiplex assays, which is to generate multiple non-overlapping emission bands at various wavelengths using a single excitation source. Such a scenario can be visualized in a Tb 3+ –Eu 3+ -co-doped ZnS NP.…”

“…Different excitation wavelengths were used by various researchers while investigating the Tb 3+* → Eu 3+ energy transfer. ,,,− For example, in some cases, the host moiety is excited, while in others, this interaction is studied by directly exciting one of the Tb 3+ direct bands. A wide range of excitation energies indicate the involvement of different initially excited electronic energy levels in investigating the inter-Ln 3+ interactions.…”

Improving the luminescence property of the novel yellow-emitting phosphor SrLa2Sc2O7:Bi3+ with charge compensators (Li+, Na+, K+) and its application in NUV-based white LEDs

“…In recent years, phosphor-converted light emitting diodes (pc-LEDs) have been expected to play a key role in the future of illumination. 1,2 Generally, pc-white LEDs synthesized with the yellow phosphor Y 3 Al 5 O 12 under blue chip excitation have a low color rendering index R a = 75 and a high correlated color temperature CCT = 7746 K, 1,3,4 and it is often necessary to add a red phosphor (CaSiAlN 3 :Eu 2+ ) to improve the color rendering index of white LEDs. With the progress of scientific research, yellow phosphors play an essential role in pc-LEDs.…”