Tunable light emission from Bi- and V-doped borosilicate glasses for application in white light-emitting diodes

A research group from Spain and Slovakia has achieved a breakthrough in the field of luminescent materials with possible application to LED lighting thanks to the publication of a paper describing the design and fabrication of borosilicate glasses doped with bismuth (Bi) and vanadium (V) capable of emitting white light consisting of a broad spectrum of all colors. These transparent and low-cost glasses have promising potential for application in future white light-emitting diodes (LEDs) with good efficiency and low power consumption.

One of the main challenges today is to reduce global energy consumption, and general lighting still accounts for a significant percentage of that energy consumption.

LEDs are an efficient and energy efficient solution in the lighting market, however, most of the white light LEDs available on the market require the combination of several materials to achieve various colors that together give white light, and this can affect their stability and efficiency. In addition, some of these currently used materials present economic and sustainability issues of concern.

In this context, borosilicate glasses doped with bismuth and vanadium present a promising alternative, never explored for white light emission. These light-emitting glasses are inorganic materials that are characterized by their ease of preparation and their ability to be manufactured in thin films compatible with industrial production methods. Borosilicate glasses offer good electrical conductivity and good mechanical properties.

The borosilicate glasses developed in this study were obtained by a relatively low temperature melting process, a method also suitable for future large-scale production. The addition of bismuth and vanadium ions (abundant and inexpensive elements) to the fabricated glasses made it possible to obtain broad spectrum emissions, covering the entire visible light range. The added bismuth ions have been found mainly in the form of Bi3+, acting as modifiers of the material properties that reduce the glass transition temperature (temperature at which an amorphous solid passes from a hard to a soft state) as its content increases.

The photoluminescence of bismuth ions shifted toward longer wavelengths as their content in the glasses increased, which was associated with the stabilization of Bi2+ and the presence of Bi3+ in different local environments. Combined with vanadium ions, the glasses showed light emission covering the entire visible spectrum, making them a promising option for white LED applications. In addition, these glasses enabled correlated color temperatures between 6135 and 4010 K to be achieved, providing quality illumination.

The development of these rare-earth-free glasses opens up new possibilities in the manufacture of energy-efficient white LEDs with good efficiency. In addition, their large-scale production and low cost make them an attractive option for general lighting. The researchers carried out a comprehensive study of the thermal, structural, compositional and optical properties of these glasses, using various analytical techniques.

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