It's been a long standing staple of Science Fiction. You know, the character with the cool shades that have a display right in the lens. A window running Windows on it. Windshield displays in cars too (great, something else to distract bad drivers). It seems once more that science fiction is again becoming science fact.

Researchers at Purdue University and Northwest University have developed a flexible and transparent transistor using a combination of zinc-oxide and indium-oxide nanowires. These invisible and bendable transistors actually preform better than conventional transistors, and can be easily built onto sheets of flexible plastic.

One of the researchers at Purdue, David Janes, said that "The transistors could lead to brighter see-through OLED (Organic Light Emitting Diode) displays."

Their work also revealed a promising new development in the control of OLED's. They found that when conformist nontransparent transistor circuitry is placed around the OLED, it could be inadvertently be emitting its own light. But these transparent transistors can actually be placed beneath the crest of the OLED. This would help to obscure the already invisible transistor, but making its light source a part of the OLED's light source. The transistor would control the OLED  as well. There is also the added benefit of less space used, bringing the hope of a higher resolution display with a small dot pitch.

In building these invisible transistors, Janes and his colleagues began by depositing indium-zinc-oxide onto glass or plastic, then applied a nanowire solution. Then, when they found the appropriate nanowire for the application, they applied a source and drain electrode to the nanowire. These source and drain electrodes helped to lock the nanowire in place and complete the electrical circuit. It should be noted that the indium-zinc-oxide and indium-tin-oxide that were used to create the source and drain electrodes are both transparent.

These invisible nanowires posses a high electron mobility rate, important in helping to determine and control the transistor speed and current capacity. Conventional transistors built from amorphous (homogeneous) silicon is only a few hundred times better when used in displays. It's the electron mobility rate that has allowed for transistors to increase in speed and decrease in size over the years.

Janes was also quick to point out that the more-compact transistors use a larger pixel area. The nanowire transistors are also very easy to fabricate when compared to silicon transistors. Silicon transistors require a high temperature process, nanowire transistors do not.

Though these zinc oxide and indium oxide transistors using nanowires look promising, carbon nanotube transistors have a far superior electron mobility rate and are far stronger. But carbon nanotube aren't transparent, due mostly to the tiny metal contacts used to connect the nanotubes. 

According to John Wager, an electrical-engineering and computer-science professor and who is also working in the area of transparent electronics at Oregon State University, for the new transistors "the performance in terms of the mobility, flexibility, and transparency is very impressive,’ and now, the biggest query that arises is, ‘Can all of this be translated into real-world maneuverability?"

The biggest hurdle to overcome however is the seemingly random nature of nanowires. Essentially, the researcher tossed down a few thousand nanowires of approximately the same size. Then, through careful observation and a lot of anticipation, they waited for the right nanowire to drift into position so they could lock it down. If they were building a large display area, this wait and see method of production wouldn't be feasible. 

Janes said further "You have to have some way of putting the desired number of nanowires in the location you want and at this point, all three technologies to make transparent transistors–nanowires, thin films, and carbon nanotubes–have a fair shot at replacing silicon transistor technology for future transparent, flexible displays."

According to John Rogers, a professor of materials science and engineering at the University of Illinois at Urbana Champaign , "it will be a good horse race to see which approach wins". But in the end, a variety of factors will decide the victor. Transparency, electrical performance, flexibility, and ease/cost of production are all considerations.

Regardless of which technology wins, the future looks pretty bright for transparent displays. Hopefully, I can get a couple sheets of these displays, put them in my windows, and have it show some really weird stuff. Maybe a shot of me talking with a cartoon character, or the inside of my house upside down, or a projection of what's in their window.