Spray-on solar cells could power your tablet

Soon, powering your tablet and other devices could be as simple as wrapping it in plastic rolls!
Researchers have invented a new way to spray solar cells on flexible surfaces using miniscule light-sensitive materials known as colloidal quantum dots (CQDs).
The advance is a major step towards making spray-on solar cells easy and cheap to manufacture, researchers said.
"My dream is that one day you'll have two technicians with Ghostbusters backpacks come to your house and spray your roof," said Illan Kramer, from the University of Toronto and IBM Canada's Research and Development Centre.
Solar-sensitive CQDs printed onto a flexible film could be used to coat all kinds of weirdly shaped surfaces, from patio furniture to an airplane's wing.

A surface the size of your car's roof wrapped with CQD-coated film would produce enough energy to power three 100-Watt light bulbs - or 24 compact fluorescents.

The system called sprayLD is a play on the manufacturing process called ALD or atomic layer deposition, in which materials are laid down on a surface one atom-thickness at a time.
Until now, it was only possible to incorporate light-sensitive CQDs onto surfaces through batch processing - an inefficient, slow and expensive assembly-line approach to chemical coating.
SprayLD blasts a liquid containing CQDs directly onto flexible surfaces, such as film or plastic, like printing a newspaper by applying ink onto a roll of paper.

This roll-to-roll coating method makes incorporating solar cells into existing manufacturing processes much simpler.
In two papers in the journals Advanced Materials and Applied Physics Letters, Kramer showed that the sprayLD method can be used on flexible materials without any major loss in solar-cell efficiency.
Kramer built his sprayLD device using parts that are readily available and rather affordable - he sourced a spray nozzle used in steel mills to cool steel with a fine mist of water, and a few regular air brushes from an art store.
"This is something you can build in a Junkyard Wars fashion, which is basically how we did it. We think of this as a no-compromise solution for shifting from batch processing to roll-to-roll," Kramer said.

"As quantum dot solar technology advances rapidly in performance, it's important to determine how to scale them and make this new class of solar technologies manufacturable," said Professor Ted Sargent, vice dean, research in the Faculty of Applied Science and Engineering at University of Toronto.
"We were thrilled when this attractively manufacturable spray-coating process also led to superior performance devices showing improved control and purity," said Sargent.