Thermal effects in (oxy)nitride phosphors

Abstract

Technologies that control the chemical composition of white lighting-emitting diodes are promising means to enhance thermal properties and renew spectra generation. Although (oxy)nitride red phosphors have been available for more than a decade, the drawbacks of these devices still evidently remain with respect to the local environments of activators in a variety of nitridosilicates. Thermal effects, such as, thermal quenching, thermal ionization, and thermal degradation, are technologically important parameters that determine product reliability. In recent years, red phosphors, which can alter novel complexes with particular wavelengths, have been easily synthesized and used to minimize losses during energy conversion process. Silicon nitride ceramics contain a more highly condensed network compared with silicate because of the higher degree of cross-linking, edge-sharing SiN 4 tetrahedron, and more covalent and stronger crystal field splitting. To provide a reasonable explanation for the relationship between photoluminescence and structure, an empirical model has been proposed, in which the changes in the chemical environment of the activators are attributed to strains resulting from atom displacements. In addition, the development of high-efficiency and cost-effective light-emitting diodes based on these luminescent materials has difficult challenges.

Carbon dot grafted SrAl2O4:Eu,Dy dual-emitting phosphor for ratiometric temperature sensing

“…The surrounding temperature can be monitored and measured by using the intensity ratio of the emission from the two thermally coupled levels. 33 In addition, the energy separation between the two levels should be small for efficient thermal coupling. Ratiometric temperature sensing is expected to be more accurate than single-parameter temperature sensing because it provides self-calibrated results from two readouts.…”

Reduced graphene oxide enwrapped phosphors for long-term thermally stable phosphor converted white light emitting diodes

“…Usually, the excess heat that is generated at the p-n junction of a blue LED does not dissipate through the phosphor layer, as these inorganic phosphors have very low thermal conductivity. Most commercial LED phosphors that have high conversion efficacy are susceptible to either thermal quenching or thermal degradation, which are serious issues that limit the lifetime of pcLEDs178. Because of this, only a limited number of phosphors–those that are most resistant to thermal quenching or thermal degradation–find application in commercial pcLEDs, even though a large number of phosphors with high conversion efficacy are available.…”

Critical Review—Narrow-Band Emission of Nitride Phosphors for Light-Emitting Diodes: Perspectives and Opportunities

“…With the temperature-dependent photoluminescence intensity of SLA (Fig. 6b), 25 the integrated light output drops by only 5% at 500 K compared to the Ce 3+ -doped garnet phosphors, and the change in chromaticity with temperature is low. arc-welded tantalum ampule under inert gas condition at 1000…”

“…With the temperature-dependent photoluminescence intensity of SLA (Fig. 6b), 25 the integrated light output drops by only 5% at 500 K compared to the Ce 3+ -doped garnet phosphors, and the change in chromaticity with temperature is low. In the temperature range of 303 to 465 K, the emission band shifts by only approximately 1 nm toward high energies while the spectrum broadens by approximately 374 cm −1 .…”