THE INFLUENCE OF TEMPERATURE ON THE SPECTRAL CHARACTERISTICS OF LEDS WITH A LUMINESCENT COATING BASED ON PHOSPHATE-TUNGSTANE GLASS-CERAMICS

Abstract

Nowadays, the light-emitting diode (LED) lamps are the most energy-efficient light-emitting devices, the emission spectrum of which can be adjusted in accordance with a specific practical task. One of the important characteristics is the stability of the emission intensity during the operation of such devices. An urgent task is the development of luminescent coatings for white LEDs based on glasses and glass ceramics, because, in comparison with polymers, they are more resistant to high temperatures and powerful light fluxes. The aim of the study was to determine the effect of temperature on the intensity and spectral composition of radiation of the combined system "UV LED + Fluorescent Glass Ceramics" (SD + LCS) and to compare the obtained data with temperature dependences of such characteristics for commercial white LEDs. In this work, the change in the intensity and spectrum of the light emission of the model combined system "UV LED + glass ceramics" when heated up to 105 ° C was studied. The results obtained were analyzed together with the dependences of the luminescence intensity on temperature for a commercial white LED. The emission spectra of the combined system contain both narrow luminescence peaks associated with transitions in europium ions and broad bands elated with the emission from the LED chip and the luminescence of the glass host. When heated, the position of the emission band of the chip is slightly shifted to the long-wavelength side, both for commercial LEDs and for model combined systems. It was also found that the temperature stability of model "white" light sources based on phosphate-tungstate glass ceramics is higher than the corresponding characteristic of commercial white LEDs in the temperature range of 50 - 105 ° C.