The halide double perovskite Cs2NaInCl6 doped with Sb3+ is shown to be a promising blue phosphor.

We unify two prevailing theories of thermal quenching (TQ) in rare-earth-activated inorganic phosphors -the cross-over and auto-ionization mechanisms -into a single predictive model. Crucially, we have developed computable descriptors for activator environment stability from ab initio molecular dynamics simulations to predict TQ under the cross-over mechanism, which can be augmented by a band gap calculation to account for auto-ionization. The resulting TQ model predicts the experimental TQ in 29 known phosphors to within ~ 10-11%. Finally, we have developed an efficient topological approach to rapidly screen vast chemical spaces for the discovery of novel, thermally robust phosphors.

The photoluminescence spectrum generated by an ordinary phosphor-converted white light-emitting diode (pc-wLED) that combines a blue LED chip with a yellow phosphor or a near-UV LED with red, green, and blue phosphors contains a notable cavity in the cyan region of the visible spectrum (480− 520 nm), which reduces the color quality produced by these lights. Here, we report a new bright blue-cyan-emitting phosphor, NaMgBO 3 :Ce 3+ , which bridges the gap. Rietveld refinements verify the rare-earth substitution while ab initio calculations prove that Ce 3+ occupies the Na + sites. NaMgBO 3 :Ce 3+ is excited by a broad range of near-UV light sources and produces a blue-cyan emission with a high (internal) quantum efficiency, minimal thermal degradation, and zero-chromaticity drift at elevated temperatures. Fabricating a near-UV (λ ex = 370 nm) pumped pc-wLED using NaMgBO 3 :Ce 3+ along with commercially available phosphors demonstrates a well-distributed warm white light with a high color-rendering index (R a ) of 91 and a low correlated color temperature (CCT) of 3645 K. Closing the cyan cavity with NaMgBO 3 :Ce 3+ is ideal for generating a pleasant, full-spectrum warm white light.

The production of white light based on a near-UV LED chip requires incorporating three inorganic phosphors that emit in the blue, green, and red portions of the visible spectrum. Using a near-UV LED has the advantage of generating a light with excellent color quality, but due to the large Stokes' shift between the LED excitation and the multiple phosphor emissions, these devices can suffer from a low overall efficiency. To minimize this inherent energy loss, the three phosphors employed to convert the LED emission must be very efficient, as measured by the internal photoluminescent quantum yield (Φ). In this work, we report the synthesis of a cubic borate, Ba 3 Y 2 B 6 O 15 , which when substituted with Ce 3+ becomes an efficient blue phosphor. This compound can be prepared using a multistep high temperature solid state synthesis with the ensuing photoluminescent measurements revealing a broad excitation band (300−415 nm) making this phosphor compatible with a 365 or 400 nm LED chip. Ba 3 Y 2 B 6 O 15 :Ce 3+ luminesces bright blue (λ em = 446 nm) and is the narrowest Ce 3+ based phosphor reported thus far with a full width at half the maximum of only 70 nm due to its highly symmetric, nearly perfect octahedral rare-earth coordination environment. Moreover, exciting Ba 3 Y 2 B 6 O 15 :Ce 3+ at 365 nm results in a Φ of 84% owing to the dense connectivity of the crystal structure. This combination of a broad excitation spectrum, narrow emission, and high Φ suggest that Ba 3 Y 2 B 6 O 15 :Ce 3+ is an excellent phosphor for incorporation in a three-phosphor, near-UV LED system. Furthermore, these results demonstrate that a highly symmetric and ordered rare-earth environment in combination with a highly connected polyhedral network is a universal design criterion to generate narrow-emitting phosphors.

The proliferation of energy-efficient light-emitting diode (LED) lighting has resulted in continued exposure to blue light, which has been linked to cataract formation, circadian disruption, and mood disorders. Blue light can be readily minimized in pursuit of “human-centric” lighting using a violet LED chip (λem ≈ 405 nm) downconverted by red, green, and blue-emitting phosphors. However, few phosphors efficiently convert violet light to blue light. This work reports a new phosphor that meets this demand. Na2MgPO4F:Eu2+ can be excited by a violet LED yielding an efficient, bright blue emission. The material also shows zero thermal quenching and has outstanding chromatic stability. The chemical robustness of the phosphor was also confirmed through prolonged exposure to water and high temperatures. A prototype device using a 405 nm LED, Na2MgPO4F:Eu2+, and a green and red-emitting phosphor produces a warm white light with a higher color rendering index than a commercially purchased LED light bulb while significantly reducing the blue component. These results demonstrate the capability of Na2MgPO4F:Eu2+ as a next-generation phosphor capable of advancing human-centric lighting.

Highly efficient, thermally stable phosphors excited by blue LEDs are crucial for energy-efficient light bulbs and modern display applications. These materials are a central component in these devices, and here one of the first Eu2+-substituted green-emitting borate phosphors is demonstrated. The green emission in NaBaB9O15:Eu2+ stems from Eu2+ occupying the smaller [NaO6] polyhedron instead of the larger [BaO9] polyhedron. This preferential substitution is identified by using quantum mechanical calculations and supported by high-resolution synchrotron X-ray powder diffraction and photoluminescence data. The resulting green emission peak is centered at 515 nm with a quantum yield of >80% (λex = 430 nm). This phosphor also exhibits negligible thermal quenching up to 650 K due to the wide bandgap, high connectivity of the rigid NaBaB9O15 crystal structure, and the depopulation of trap states stemming from the aliovalent rare-earth substitution. Fabricating two blue light pumped LED prototypes with NaBaB9O15:Eu2+ as the green component and a second red-emitting phosphor demonstrates this novel material’s capabilities in both display and warm white lighting formats. Alongside the outstanding optical properties, the accessible synthetic conditions and cost-effective starting materials suggest the remarkable potential of NaBaB9O15:Eu2+ in next-generation LED-based lighting or display systems.

One of society’s grand challenges is to reduce energy usage in ways that are cost-effective, sustainable, and environmentally benign. Replacing incandescent and compact fluorescent light bulbs with energy-efficient, solid-state white lighting is one of the easiest and most promising solutions. Eu3+-substituted inorganic oxide phosphors are one class of materials that can serve as the red component in these new light bulbs, allowing the creation of warm white light. Unfortunately, the emission intensity in most of these materials cannot be reliably maintained at elevated temperatures. There is therefore a need to discover entirely novel phosphor materials that are thermally robust; however, this is generally a prolonged and expensive process requiring extensive synthetic effort. In this work, we develop a machine-learning regression algorithm based on 134 experimentally measured temperature-dependent Eu3+ emission data points to rapidly estimate the thermal quenching temperature (T 50), which is defined as the temperature when the emission intensity is half of the initial value. The T 50 was then predicted for more than 1000 potential oxide Eu3+ phosphor hosts using this model. Five compounds with predicted thermal quenching temperatures >423 K were subsequently selected and synthesized for validation of this approach. The phosphors, Sr2ScO3F, Cs2MgSi5O12, Ba2P2O7, LiBaB9O15, and Y3Al5O12, all exhibit good thermal stability when substituted with Eu3+, suggesting the success of our methodology.

Perovskites are a class of materials with applications in photovoltaics, solid-state lighting, and catalysis. Extensive research has gone into modifying the chemical composition of these distortion-prone structures to manipulate and achieve their tremendous physical properties. Here, we report a BaScO2F perovskite that, when doped with Eu2+, produces a highly efficient cyan emission stemming from the structure’s high symmetry and dense connectivity. However, the emission peak is broader than expected and steady-state, temperature-dependent, and time-resolved photoluminescence spectroscopy reveals the presence of two distinct emission peaks despite a single rare-earth substitution site. Ab initio calculations subsequently prove that substituting the smaller Eu2+ induces an unexpected local structure distortion driven by zone-boundary octahedral tilting. This produces two different local coordination environments around Eu2+ that cause the dual emission. This work shows the critical need to analyze local distortions in phosphors upon rare-earth substitution, especially in perovskites on the verge of structural instabilities.