Phosphor-converted white light-emitting diodes (pc-WLEDs) are efficient light sources used in lighting, high-tech displays, and electronic devices. One of the most significant challenges of pc-WLEDs is the thermal quenching, in which the phosphor suffers from emission loss with increasing temperature during high-power LED operation. Here, we report a blue-emitting NaSc(PO):xEu phosphor (λ = 453 nm) that does not exhibit thermal quenching even up to 200 °C. This phenomenon of zero thermal quenching originates from the ability of the phosphor to compensate the emission losses and therefore sustain the luminescence with increasing temperature. The findings are explained by polymorphic modification and possible energy transfer from electron-hole pairs at the thermally activated defect levels to the Eu 5d-band with increasing temperature. Our results could initiate the exploration of phosphors with zero thermal quenching for high-power LED applications.

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We have developed a hybrid phosphor-in-glass plate (PGP) for application in a remote phosphor configuration of high-power white light emitting diodes (WLEDs), in which single-layer graphene was used to modulate the thermal characteristics of the PGP. The degradation of luminescence in the PGP following an increase in temperature could be prevented by applying single-layer graphene. First, it was observed that the emission intensity of the PGP was enhanced by about 20% with graphene wrapping. Notably, the surface temperature of the graphene-wrapped PGP (G-PGP) was found to be higher than that of the bare PGP, implying that the graphene layer effectively acted as a heat dissipation medium on the PGP surface to reduce the thermal quenching of the constituent phosphors. Moreover, these experimental observations were clearly verified through a two-dimensional cellular automata simulation technique and the underlying mechanisms were analyzed. As a result, the proposed G-PGP was found to be efficient in maintaining the luminescence properties of the WLED, and is a promising development in high power WLED applications. This research could be further extended to generate a new class of optical or optoelectronic materials with possible uses in a variety of applications.

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