Stories tagged thin films

Feb
21
2010

Solar cells made from common materials

Solar cells for everyone
Solar cells for everyoneCourtesy Dominic

Solar cells produce less than 1/1000 of the Earth's electricity. This is mainly because they are expensive and are made from rare, hard to obtain materials.
An IBM research team, managed by David Mitzi, is working on photovoltaic cells that are made from common materials.

The new solar cells are also cheaper to manufacture, using a “printing” technique that uses a hydrazine solution containing copper and tin with nanoparticles of zinc dispersed within it. The solution is then spin-coated and heat treated in the presence of selenium or sulfur vapor. PhysOrg

9.6% Efficiency

This new material, called kesterite, was 6.8% efficient in 2009. IBM increased the efficiency to 9.8% and is planning to increase the efficiency above 11 per cent, which is equal to or better than the traditional solar cells.

Abstract of published paper: High-Efficiency Solar Cell with Earth-Abundant Liquid-Processed Absorber Advanced Materials

Nov
02
2007

Nanotechnology sometimes borrows from nature.

Morpho butterfly: Pigments don’t cause these butterflies’ intense colors. Instead, super-small lattice-like structures on the wings reflect only certain wavelengths of light (or color). And the colors shift with your perspective. (Photo courtesy Lionoche, through Flickr)
Morpho butterfly: Pigments don’t cause these butterflies’ intense colors. Instead, super-small lattice-like structures on the wings reflect only certain wavelengths of light (or color). And the colors shift with your perspective. (Photo courtesy Lionoche, through Flickr)

Super-small, light-reflecting structures—instead of pigments—create a morpho butterfly's intense, iridescent wing color. Scientists are developing nanomaterials with similar properties.

Zoom in on a butterfly's wing
Zoom in on a butterfly's wing

If you used a special microscope to look at these butterfly wings, you’d see tiny scales made up of thin layers of transparent wing material with nanoscale gaps between them. Light waves bouncing off the bottom surfaces interfere with waves reflecting from the tops. Most light waves are cancelled and only certain wavelengths—or colors—bounce back to your eyes. The more light in the environment, the brighter the color.

Wing structures: These complicated structures on butterfly wings manipulate light to control the color that we see.
Wing structures: These complicated structures on butterfly wings manipulate light to control the color that we see.

How do transparent thin films create color?: Scientists haven't yet created materials that work exactly like the butterfly wings. But layers and layers of transparent, super-thin films--each with a different index of refraction--can be tuned so that they only reflect specific wavelengths of light (o
How do transparent thin films create color?: Scientists haven't yet created materials that work exactly like the butterfly wings. But layers and layers of transparent, super-thin films--each with a different index of refraction--can be tuned so that they only reflect specific wavelengths of light (o

Scientists are developing all sorts of products that, like the butterfly wings, use layers of transparent materials with nanoscale spacing between them to manipulate light and create color. With them, we can create computer and cell phone displays, fabrics and paints that change color, optical devices that improve telecommunications systems, and films that reflect much more light than glass mirrors. Can you imagine other uses?

Mar
09
2007

New nano material a black hole for reflections.

Silica nanorods make a super dark surface.: This SEM image shows the silica nanorods mounted at exactly 45 degrees which makes the surface super anti-reflective.
Silica nanorods make a super dark surface.: This SEM image shows the silica nanorods mounted at exactly 45 degrees which makes the surface super anti-reflective.

Scientists at Rensselaer Polytechnic Institute have created a material that reflects virtually no light. By depositing layers of silica nanorods at an angle of 45 degrees on top of a thin film of aluminum nitride, a new world record has been set for anti-reflective surfacing.

The technique allows the researchers to strongly reduce or even eliminate reflection at all wavelengths and incoming angles of light, Schubert said. Conventional anti-reflection coatings, although widely used, work only at a single wavelength and when the light source is positioned directly perpendicular to the material. PhysOrg.com

Where will this make a difference?

The new optical coating could find use in just about any application where light travels into or out of a material, such as:

  • More efficient solar cells
  • Brighter LEDs
  • High-reflectance mirrors
  • Black body radiation
  • Optical interconnects (photonics)

RPI press release here:

Rensselaer Polytechnic Institute press release