Variation from Zero to Negative Thermal Quenching of Phosphor with Assistance of Defect States

A novel blue emitting phosphor Ca1-ySryScBO4:Bi3+ with zero-thermal quenching for multi-scenario application

In recent years, Bi3+ activated phosphors have received a lot of attention from researchers; however, the performance and application areas of phosphors are yet to be developed. In this work, a series of CaScBO4(CSBO):xBi3+ phosphors were successfully prepared using a high-temperature solid-state method. Under UV excitation, blue light emission was achieved at 430 nm with a quantum yield of 91%, and at 423 K, the emission intensity retained 82.8% of the original intensity at 298 K. By crystal field engineering, the substitution of Sr2+ at the Ca2+ site enhances the temperature stability of the material, and at 423 K, 473 K and 573 K, the samples maintain 104%, 103% and 85% of the emission intensity at room temperature, respectively. It indicates that the cation substitution causes the increase in the oxygen vacancy concentration, and the oxygen vacancy defect compensates the energy lost in electrons at high temperature, producing resistance to anti-TQ performance. Finally, a blue-violet LED was fabricated by using the phosphor and an ultraviolet LED chip, and white LEDs (CCT = 4683 K, Ra = 89.7) were obtained by co-packaging this phosphor with commercial phosphors and a UV chip. Importantly, the great potential of this phosphor in the field of plant lighting and biocontrol can be demonstrated.

High-Efficiency Continuous-Luminescence-Controllable Performance and Antithermal Quenching in Bi3+-Activated Phosphors

Recently, Bi³⁺-activated phosphors have been widely researched for phosphor-converted light-emitting diode (pc-LED) applications. Herein, novel full-spectrum A₃BO₇:Bi³⁺ (A = Gd, La; B = Sb, Nb) phosphors with a luminescence-tunable performance were achieved by a chemical substitution strategy. In the La₃SbO₇ host material, a new luminescent center was introduced, with Gd³⁺ replacing La³⁺. The photoluminescence (PL) spectra show a large blue shift from 520 to 445 nm, thus achieving regulation from green to blue lights. Moreover, a series of solid solution-phase phosphors La₃Sb_1-xNb_xO₇:Bi³⁺ were prepared by replacing Sb with Nb, and a PL spectral tunability from green (520 nm) to orange-red (592 nm) was realized. Temperature-dependent PL spectra show that La_3-xGd_xSbO₇:Bi³⁺ phosphors have excellent thermal stability. Upon 350 nm excitation, the PL intensity of La_3-xGd_xSbO₇:Bi³⁺ phosphors at 150 °C remained at more than 93% at room temperature. With Gd³⁺ doping, the thermal stability gradually improved, and LaGd₂SbO₇:0.03Bi³⁺ represents splendid antithermal quenching (135.2% at 150 °C). Finally, a full-visible spectrum for pc-LED with a high color-rendering index (Ra = 94.4) was obtained. These results indicated that chemical substitution is an effective strategy to adjust the PL of Bi³⁺, which is of great significance in white-light illumination and accurate plant lighting.

Modulation of Thermally Stable Photoluminescence in Cr3+-Based Near-Infrared Phosphors

Broadband near-infrared (NIR) light sources based on phosphor-converted light-emitting diodes (pc-LEDs) are desirable for various photonics applications, while developing thermally stable NIR phosphors remains a great challenge. Increasing the temperature accelerates the severe nonradiative relaxation process gorverned by the intrinsic energy gap law, which further suspends the efficient low-energy emission of Cr³⁺ emitters in the inorganic lattice. To address this rule, several state-of-the-art strategies have been put forward in this perspective to modulate the critical law from the viewpoints of (1) crystal structure design, (2) defect engineering, (3) strengthened rigidity, and (4) energy transfer. This perspective suggests avenues for exploring novel broadband NIR phosphors with high thermal stability and will also stimulate further studies on NIR spectroscopy for high-power applications.

Multiple Charge Transfer Bands Induced Broad Excitation Eu3+ Red Emission in a Vanadium Phosphate System for White Light-Emitting Diodes

In order to realize broad excitation and narrow emission red light phosphor, a new vanadium phosphate Ba₂BiV₂PO₁₁ was selected as a host for Eu³⁺. Monitored at 619 nm, a wide band from 240 to 400 nm could be observed and inferred to be composed of Eu³⁺-O^2- and V⁵⁺-O^2- charge transfer bands, which could make it match well with the UV chip and the blue chip along with the characteristic excitation of Eu³⁺ at 465 nm. Under 354 nm excitation, the sample could emit high color purity red light, and the thermal quenching integral intensity showed good thermal stability. The generation of charge transfer bands was investigated in detail combined with the luminescence properties and the structure of the matrix. Moreover, the as-prepared phosphor could improve the white light performance of blue chip-activated YAG:Ce³⁺ and n-UV chip-activated tricolor phosphors. All the results indicated the multiple application potential of Ba₂BiV₂PO₁₁:Eu³⁺ for white light-emitting diodes.