Cheap TiO2 fabrication yields boosted LEDs, solar cells
Sandia National Laboratories has come up with a cheap method to synthesise titanium-dioxide (TiO2) nanoparticles, which could yield enhanced devices including LEDs and solar cells.
While the industry has largely shunned TiO2 nanoparticles because they have been difficult and expensive to make, 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, like dish soap does with fat. These methods produce less-than-ideal nanoparticles that are very expensive, can vary widely in size and show significant particle clumping, called 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.
"We wanted something that was low cost and scalable, and that made particles that were very small," said researcher Todd Monson, who along with principal investigator Dale Huber patented the process in mid-2011 as "High-yield synthesis of brookite TiO2 nanoparticles."
Their method produces nanoparticles roughly 5nm in diameter, approximately 100 times smaller than the wavelength of visible light, so there's little light scattering, Monson said.
TiO2 can increase the refractive index of materials, such as silicone in lenses or optical encapsulants. Refractive index is the ability of material to bend light. Eyeglass lenses, for example, have a high refractive index.
Practical nanoparticles must be able to handle different surfactants so they're soluble in a wide range of solvents. Different applications require different solvents for processing.
Sandia National Laboratories researchers Dale Huber, left, and Todd Monson have come up with an inexpensive way to synthesise titanium-dioxide nanoparticles, which could be used in everything from solar cells to light-emitting diodes. Source: Randy Montoya, Sandia