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

• Published in: Journal of physical chemistry. C 2021-03, Vol.125 (11), p.6163-6175
• Main Authors: Rastogi, Chandresh Kumar, Sharma, Shilendra Kumar, Sasmal, Sayantan, Pala, Raj Ganesh S, Kumar, Jitendra, Sivakumar, Sri
• Format: Article
• Language: English
• Subjects: C: Spectroscopy and Dynamics of Nano, Hybrid, and Low-Dimensional Materials
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/acs.jpcc.0c10294

Incorporation of suitable lanthanide (Ln3+) ions into semiconducting WO3 can be useful to produce host-sensitized luminescence for solid-state lighting applications. Codoping of another Ln3+ ion can assist in transferring energy from the host to the activator Ln3+ ion to produce bright luminescence depending upon the electronic structure of the doped system. As a case study, Eu3+ and Tb3+ ion–doped WO3 phosphors (WO3:Tb3+ x Eu3+ 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 Tb3+ ion as a sensitizer and realize host-sensitized emission from Eu3+ ions. The steady-state and time-resolved photoluminescence (TRPL) data for WO3:Tb3+ x Eu3+ y (x = 0–0.05 and y = 0–0.10) samples confirm that Tb3+ ions assist in excitation of Eu3+ ions via sequential energy transfers from the host to Tb3+ ions followed by Tb3+ to Eu3+ ions. The energy transfer process is controlled by optimizing their doping concentrations, and a single-phase white-light-emitting phosphor with a composition WO3:Tb3+ 0.05Eu3+ 0.0005 has been developed. The electronic band structures and projected density of state plots for the WO3:Tb3+ 0.03125Eu3+ 00.03125 system obtained using density functional theory (DFT)-based simulations confirm the formation of impurity states due to Eu3+ and Tb3+ ions within the forbidden gap of WO3. Based on the TRPL and DFT data, it is confirmed that the Tb3+ ions act as a bridge between the conduction band edge of WO3 and excited states of Eu3+ ions to transfer energy and facilitate characteristic emission from europium species.