Bi-containing molybdate glass-ceramics as luminescent coating for elaboration of white light emitting diodes

Authors

  • V. Chornii National University of Life and Environmental Sciences of Ukraine image/svg+xml
  • V. Boyko National University of Life and Environmental Sciences of Ukraine image/svg+xml
  • O. Pan’ko National University of Life and Environmental Sciences of Ukraine image/svg+xml
  • S. Nedilko Taras Shevchenko National University of Kyiv image/svg+xml
  • M. Slobodyanik Taras Shevchenko National University of Kyiv image/svg+xml
  • K. Terebilenko Taras Shevchenko National University of Kyiv image/svg+xml
  • V. Scherbatskyi Taras Shevchenko National University of Kyiv image/svg+xml

DOI:

https://doi.org/10.31548/energiya2019.06.122

Abstract

Abstract. The lamps, those consist of white light emitting diodes are energy-effective source of light for outdoor and in-house illuminations. Such LEDs, as usual, consist of semiconductor chip and phosphor that coated on chip with usage of some polymer. The deterioration of optical properties of polymer during LED operation leads to decreasing of energy-effectiveness of the device after some time. Substitution of polymer by glass-ceramics allows to overcome the abovementioned drawback. In present paper the results of the study of morphology and optical properties of the set of Bi-containing molybdate glass-ceramics are reported. All the samples were characterized by scanning electron microscopy, UV-Vis and luminescent spectroscopy methods. Although fast cooling procedure it was found that depending on composition of initial melt the samples of glass-ceramics contain rectangular and/or needle-like crystallites those can be probably K2Mo2O7 and V2O5, respectively. Increasing of potassium and phosphorus content in initial melt leads to increasing of reflectance of the samples. In the same time, increasing of vanadium content leads to significant decreasing of reflectance of the samples. Taking into account relation between absorbance and reflectance, which can be described by Kubelka-Munk’s formula, it was concluded that all the glass-ceramics samples have strong absorption in the spectral regions, where wavelength is below 415 nm. The studied samples reveal complex wide-band photoluminescence in visible spectral region under excitation at 405 nm at room temperature. Two bands with maxima near 580 and 650 nm are inherent for all the samples. The band in blue spectral region with maximum at 450 nm was clearly observed for sample with phosphorus. Bands in blue and green spectral regions can be ascribed to Bi3+ ions in oxygen surrounding, while band in red region is related with emission centers those are based on molybdate anionic groups. Optical properties of the studied samples, excluding one with vanadium, indicate the possibility to use these glass-ceramics for elaboration of white LEDs. Further improvement of optical characteristics of the Bi-containing glass-ceramics can be performed through increasing of content of alkali metals or/and phosphorus in melt.

Key words: photoluminescence, glass-ceramics, bismuth, reflection spectra

References

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Published

2020-02-12

Issue

No. 6 (2019)

Section

Статті

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