Currently, lanthanide (Ln 3+ ) doped double perovskites (DPs) suffer from poor controllability of doping and the high concentration quenching phenomenon. Herein, a novel efficient energy transfer (ET) host of Cs 2 NaLuCl 6 Rare-earth-based (RE-based) DPs via Ag + /Bi 3+ co-doping for further Ho 3+ doping is developed. Benefiting from Ag + /Bi 3+ - manipulated the parity of the wavefunction of the self-trapped exciton, intense self-trapped excitons (STEs) broadband warm white visible emission is boosted. Specifically, photoluminescence quantum yield (PLQY) of co-doping with Bi 3+ and Ag + ions in Cs 2 NaLuCl 6 under 350 nm excitation is dramatically promoted to 86.19 % with half maximum (FWHM) of 224 nm. Although the pristine crystal Cs 2 NaLuCl 6 exhibits intrinsic blue emission with FWHM of 75 nm. Furthermore, the ET channel from STEs to Ho 3+ was constructed by tri-doping Ho 3+ , and the effective red and near-infrared (NIR) emission of Ho 3+ was obtained. Finally, NIR light-emitting diodes (LEDs) and white LED based on Ho 3+ doped/undoped Cs 2 Na 0.8 Ag 0.2 Lu 0.98 Bi 0.02 Cl 6 DPs were prepared with different application features. Specifically, white LEDs showed higher color rendering index and lower associated color temperature, while NIR LEDs showed good night vision imaging. This work provides a new strategy for the design of an ET host suitable for Ln 3+ doping, avoiding the effects of the concentration quenching phenomenon that always occurs in heavily doped hosts and realizing controllable doping.
Zhao Caiyue,Xu Yudong,Wang Lei,Chen Xinyi,Hu Wenjie,Dai Zhaoxiang,Hu Mengyuan,Liu Kai,Shi Min
In this study, Bi 3+ and Mn 4+ co-doped CaAl 12 O 19 phosphors were prepared via high-temperature solid-state reaction method, and their crystal structure, particle morphologies, luminescence properties, charge compensation mechanism and crystal field effect were investigated in detail. A most remarkable tuning effect can be achieved when the Bi 3+ concentration is 5% in CaAl 12 O 19 :Bi 3+ , 0.05% Mn 4+ and the electric multipolar interaction is inferred to be the main mechanism for concentration quenching effect. It is also found that, as charge compensators rather than sensitizers, Bi 3+ ions can effectively tailor the emissions in a wide range through partial reducing Mn 4+ to Mn 2+ . The charge compensation physics presumably involves the shift of Fermi energy level ( E F ) and variations of valence states of manganese ions after Bi 3+ introduction. Moreover, the authors calculated the splitting energy (Δ) and Racah parameters ( B and C ) for Mn 4+ in octahedral sites and Mn 2+ in tetrahedral sites by combining excitation spectra with Tanabe-Sugano diagram. The experimental results will be of certain helpfulness in developing phosphors used in white LED.
Long afterglow phosphors have garnered significant attention for their ability to emit light long after excitation ceases. Afterglow emission relies on metastable trap levels within the bandgap of the host materials. Effective trap engineering strategies to optimize traps are critical in determining the afterglow performance. In this study, we investigate the codoping of Bi 3+ and Er 3+ into LiTaO 3 to enhance afterglow performance. Through high-temperature solid-state synthesis, a series of LiTaO 3 :x%Bi 3+ , y%Er 3+ (x = 0 or 0.5%, y = 0.1–4.0%) samples were prepared successfully. Structural characterization confirmed the successful incorporation of Bi 3+ and Er 3+ into the Li⁺ sites without disrupting the host lattice. Photoluminescence studies revealed that Bi³⁺ codoping significantly enhances the green emission of Er³⁺, with optimal performance achieved at 1.0% Er 3+ doping. Thermoluminescence (TL) analysis demonstrated the presence of traps with the depth of 0.748 eV, enabling prolonged afterglow emission at room temperature. The afterglow mechanism involves charge carrier storage in traps under UV excitation, followed by thermal release and recombination at luminescent centers, facilitated by energy transfer from Bi 3+ to Er 3+ . This work provides a strategy for designing a long afterglow phosphor through controlled codoping, offering insights into trap engineering and energy transfer processes in perovskite-based luminescent materials.
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