Low-cost TiO2 nanoparticles promise improved optical devices

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Sandia National Laboratories has come up with an inexpensive way to synthesise titanium dioxide nanoparticles and is seeking partners who can demonstrate the process at industrial scale, for everything from solar cells to LEDs.

Titanium dioxide (TiO2) nanoparticles show great promise as fillers to tune the refractive index of anti-reflective coatings on signs and optical encapsulants for LEDs, solar cells and other optical devices.

Current production methods for TiO2 often require high-temperature processing or costly surfactants — molecules that bind to something to make it soluble in another material. Those methods produce nanoparticles that are expensive, can vary widely in size and show significant agglomeration.

Sandia’s technique, on the other hand, uses readily available, low-cost materials and results in nanoparticles that are small, roughly uniform in size and don’t clump together. The method produces nanoparticles roughly 5nm in diameter, approximately 100 times smaller than the wavelength of visible light, so there’s little light scattering, researcher Todd Monson said.

Scattering decreases the amount of light transmission. Less scattering also can help extract more light, in the case of an LED, or capture more light, in the case of a solar cell. TiO2 can increase the refractive index of materials, such as silicone in lenses or optical encapsulants.

The next step is to demonstrate synthesis at an industrial scale, which will require a commercial partner. Sandia would synthesise a small number of particles, then work with a partner company to form composites and evaluate them to see if they can be used as better encapsulants for LEDs, flexible high-index refraction composites for lenses or solar concentrators. ‘I think it can meet quite a few needs,’ Monson said.