http://www.digitaljournal.com/article/324655

University of Southern California Develops Printable Solar Cells

Posted May 10, 2012 by Yani Smith
The path for cheap solar energy has been paved, but we can't walk it just yet. Scientists at the University of Southern California (USC) have developed a liquid solar cell which they say can essentially be printed onto surfaces of any shape.
Microsope
Microsope
File Photo
The group believes the solar conduction method that has the potential to be cheaper, and more flexible than anything we have today.
The method uses solar nanocrystals so small that 250 billion would fit on the head of a pin.
Each crystal measures just four nanometers in size.
Crystals are immersed in a liquid solution, meaning they can be printed onto surfaces of essentially any shape.
"Like you print a newspaper, you can print solar cells," said Richard L. Brutchey, assistant professor of chemistry at the USC Dornsife College of Letters, Arts and Sciences.
The printable solar cells differ to traditional monocrystalline silicon cells as they are microscopic nanocrystals.
Normally these nanocrystals would not be stable enough to provide solar energy. But, David Webber, one of the inventors, created a new semiconductor coating for the cells using cadmium selenide.
The cadmium selenide semiconductor gives the solar cells the stability they need to exist as a liquid.
The cadmium selenide also assists in transferring the current from one cell to another, forming a veritable network of power between each nanocrystal.
Cost has always been the achilles’ heel of solar technology however the liquid cells can reportedly be fabricated for a lower price than monocrystalline silicon cells.
The method is not yet market-ready, but could be a potential game-changer for the future of solar.
One area that the team are working on is finding an alternative to cadmium, which is above accepted commercial toxicity levels.
Scientists from University of Notre Dame published a similar method in December 2011 – a one-coat solar paint.
Like the printable solar cells, the paint breakthrough requires further development before being market-ready.
The paint method was reported to have a conversion efficiency of around 1%, compared to traditional monocrystalline silicon cells which have recorded levels of around 24% efficiency.