Thin Film Transistor
circuit such as an OFET. See Field Effect Transistor.
The first choice of thin film semiconductor was thin film silicon decades ago and many companies still work with this material. Indeed it has been commercialised as drive circuits
on the glass substrates used for Liquid Crystal Displays (LCD
) and, more recently, Organic Light Emitting Diode (OLED) displays for such things as cellphones. The main advantage is that they are cheaper than silicon chips when used over a wide area and their inferior electrical properties are not a limitation in this application.
However, silicon thin films cannot be printed. They call for vacuum technology which is not easily made into a reel to reel flow line process. High temperatures are usually used meaning expensive or brittle substrates such as polyimide film and glass. They cannot therefore be made extremely cheap and they cannot easily compete with silicon chips for most of the envisaged low cost applications. True, in 2002, Toshiba demonstrated thin film silicon transistor circuits driving displays on glass that was quite flexible because it was very thin but this is scarcely a suitable solution for packaging. Seiko Epson are researching depositing thin film silicon TFTs on the necessary high temperature substrates then peeling them off and putting them on packaging grade materials but this strikes us as difficult, expensive and not likely to be realised commercially anytime soon.