Recent advances in Bi3+-activated narrow-band emitting phosphors for backlight display applications

The development of novel narrow-band emitting phosphors with high efficiency and stability is of great significance for WLED backlights. In recent years, the research on Bi3+-activated narrow-band emitting phosphors has gained significant attention for developing novel phosphors for WLED backlight applications. This Frontiers article presents recent advances in Bi3+-activated narrow-band emitting phosphors, encompassing their coordination environment and photoluminescence properties. The latest advancements in Bi3+-activated narrow-band emitting phosphors are categorized into four types based on host materials: germanate, silicate, borate, and other hosts. Additionally, detailed discussions are provided on the challenges associated with developing novel Bi3+-activated narrow-band emitting phosphors and potential research directions for future work. Overall, the Bi3+-activated narrow-band emitting phosphors have demonstrated great potential for WLED backlights; however, significant efforts are still required to enhance their comprehensive performance in order to meet practical application requirements.

Investigation of multicolor emitting Cs3GdGe3O9:Bi3+,Eu3+ phosphors via energy transfer for WLEDs

Bi³⁺/Eu³⁺ doped Cs₃GdGe₃O₉ luminescent materials were prepared by a solid-state reaction. The energy band and density of states of Cs₃GdGe₃O₉ were calculated by density functional theory. The Cs₃GdGe₃O₉ host presents a broadband emission peaking at 520 nm. Systemic measurement and analysis of luminescence properties were performed to confirm the energy transfer in Cs₃GdGe₃O₉:Bi³⁺,Eu³⁺. The multicolor modulated emission from blue (0.1678, 0.1568) to red (0.5931, 0.3251) can be achieved by varying the doping ratio of bismuth to europium. A white light-emitting diode (WLED) was produced by combining the Cs₃GdGe₃O₉:0.05Bi³⁺,0.1Eu³⁺ phosphor, a commercial green phosphor, and a 310 nm ultraviolet chip. The color rendering index of the WLED driven by 20 mA bias current is 89.6 with the CIE coordinates of (0.3520, 0.3626). The results reveal that the Cs₃GdGe₃O₉:Bi³⁺,Eu³⁺ phosphor is a potential material that can be used in multicolor tunable luminescence and WLEDs.

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 this work, a novel yellow-emitting phosphor SrLa2Sc2O7:Bi3+ was synthesized by high temperature solid-state method, ranging from 400 nm to 800 nm under near-ultraviolet (NUV) excitation and the full width at half maximum (FWHM) of up to 180 nm.

Luminescence property improvement and controllable color regulation of a novel Bi3+ doped Ca2Ta2O7 green phosphor through charge compensation engineering and energy transfer

In pursuit of warm WLEDs, exploration of novel phosphors and regulation of the existing phosphors are the two approaches usually used in the luminescent material field. In this work, we prepared green Ca₂Ta₂O₇:Bi³⁺ phosphors firstly and investigated their properties in detail. The as-prepared Ca₂Ta₂O₇:Bi³⁺ exhibits intense green emission in the 450-580 nm range under UV excitation, which matches well with the UV chip and can efficiently avoid the re-absorption problem. The improvement in the emission intensity and thermal stability of the phosphor was achieved using different charge compensation methods including codoping alkali metal ions (Li⁺, Na⁺, and K⁺), creating a cation vacancy, and host co-substitution (Ca²⁺ + Ta⁵⁺ → Bi³⁺ + Si⁴⁺, Ca²⁺ + Ta⁵⁺ → Bi³⁺ + Ge⁴⁺). Through systematic research, the emission intensity at room temperature was improved 2.1 times and the thermal stability was improved 2.9 times at 200 °C. By coating the prepared green sample with other commercial phosphors on the UV chip, warm WLEDs with Ra being 91.1 and CCT being 3990 K were obtained. Moreover, taking the Bi³⁺ → Eu³⁺ energy transfer strategy, the emitting color of the phosphor was tuned and yellow emitting phosphor was obtained. Our study indicates that Bi³⁺ doped Ca₂Ta₂O₇ might be a potential UV excited green phosphor for WLEDs. The charge compensation methods and the Bi³⁺ → Eu³⁺ energy transfer approach are valuable ways to improve and adjust the luminescence properties, which can further derivate a series of novel phosphors for improving the quality of WLED devices.

Enhanced photoluminescence and energy transfer behavior in Ba3Lu4O9:Bi3+,Eu3+ for flexible lighting applications

In this work, we report a color-tunable green-orange-emitting phosphor by introducing Bi³⁺ and Eu³⁺ into Ba₃Lu₄O₉ host lattice. The emission spectra of Ba₃Lu₄O₉:Bi³⁺,Eu³⁺ cover the whole visible spectral region, and present both the typical emissions from ³P₁ - ¹S₀ transitions of Bi³⁺ and ⁵D_0,1 - ⁷F_J transitions of Eu³⁺. The energy transfer behavior in the phosphor has been verified, based on which the emitting color of Ba₃Lu_4(0.98-y)O₉:0.08Bi³⁺,4yEu³⁺ (y = 0-0.08) can be tuned from yellowish green (0.3188, 0.4491) to orange (0.5304, 0.3871). The phosphor Ba₃Lu_3.6O₉:0.08Bi³⁺,0.32Eu³⁺ shows 33.3% improvement in emission intensity of Eu³⁺ compared with that of Ba₃Lu_3.92O₉:0.32Eu³⁺. Moreover, soft polydimethylsiloxane/phosphor composite films were prepared utilizing the Ba₃Lu₄O₉:Bi³⁺,Eu³⁺. Intense green-orange emissions suggest that the phosphors and corresponding s-PDMS-based films can be considered as promising candidates for near-UV pumped lighting and flexible devices.

Three mixed-alkaline-metal borates with {Li@B12Ox(OH)24−x} (x = 18, 22) clusters: from isolated oxoboron cluster to unusual layer

The isolated {Li@B12O18(OH)6} clusters are extended to the {Li@B12O22(OH)2} layer through condensation reactions for the first time.

Five new rubidium borates with 0D clusters, 1D chains, 2D layers and 3D frameworks

By tuning the synthetic conditions, borates with 0D clusters were transformed into a 1D chain, 2D layer and 3D framework.