Researchers at the University of Toronto have created a semiconductor device that outperforms today’s conventional chips — and they made it simply by painting a liquid onto a piece of glass. This is the first a so-called “wet” semiconductor device has bested traditional, more costly grown-crystal semiconductor devices. The Toronto team instead cooked up semiconductor particles in a flask containing extra-pure oleic acid, the main ingredient in olive oil. The particles are just a few nanometres (one billionth of a metre) across. The team then placed a drop of solution on a glass slide patterned with gold electrodes and forced the drop to spread out into a smooth, continuous semiconductor film using a process called spin-coating. They then gave their film a two-hour bath in methanol. Once the solvent evaporated, it left an 800 nanometre-thick layer of the light-sensitive nanoparticles.
At room temperature, the paint-on photodetectors were about ten times more sensitive to infrared rays than the sensors that are currently used in military night-vision and biomedical imaging. “These are exquisitely sensitive detectors of light,” says Sargent, who holds a Canada Research Chair in Nanotechnology. “It’s now clear that solution-processed electronics can combine outstanding performance with low cost.”