Organic electronic OTFT technology- Orgalight

Electronic Devices : OTFT
Another class of organic electronic devices is Organic Thin Film Transistor (OTFT). They are made of organic semiconductors and the first one was made from Polyacetylene in 1975. Since, several other materials were used; in 1990 it was the polythiophene (P3HT) followed by pentacene in 1997, afterwards, this kind of devices has made impressive progress over the past decade.
These organic transistors have two prime advantages over classical inorganic ones: they can be fabricated at a lower temperature which allows them to be made on a low cost plastic substrate, resulting in a flexible device which is unbreakable and very low-weight
Nowadays, OTFT performances become similar to the ones which are made with silicon, this provides a large application range for this kind of devices. For example, they will be suitable for pixel-access in OLED/PLED technology or as switching devices for logic gate memory arrays in smart card and other integrated circuits. These pictures bellow give a good idea of OTFT :

How are they made ?
Once the gate oxide is made over silicon, we can have only two ways to make source-drain contact. One called "Bottom Gate-Bottom Contact" (BG-BC), where drain and source contact (metal such as gold and other) are patterned on the gate dielectric layer before the active one deposition. The second way of fabrication is called "Bottom Gate-Top Contact" (BG-TC), in that case, both source and drain are deposited on top of the active organic layer. Here is a picture which shows, bottom contact and top contact, respectively left to right :

Which kinds of organic materials are used for this application?
As the ones used in other electronic technology (e.g. PLED or Solar Cells) we have first, electron acceptor materials (p-type) which are commonly carbon aromatic cycle structure based, and secondly, electron donor materials (n-type) that are conjugated molecules or polymers. The most common structures are shown below :

All these materials have advantages and disadvantages, therefore, some compromises have to be done between easiest fabrication and performances. For example, Pentacene has a very good capability for hole transporting, but it has a very low solubility so it must be patterned by evaporation (CVD). On the other hand, a polymer like MEH-PPV is pretty soluble in various organic solvents and can be deposited by spin coating or inkjet technique, but it has a low mobility of positive charge.
Polythiophene such as P3HT (regioregular) is currently the organic polymer the most efficient for this application, but research makes progress every day and now, a new family of conjugated polymers based on polyfluorene derivative becomes very interesting by their good performances and promises us a great progress in OTFT in a near future. For more information, especially how they work, just have a look at our link page.
To close this page of information, I will just add another electronic device, which is organic Laser. This new application for organic material came from Bell Laboratory in USA, which made a Laser from Tetracene in the year 2000. This device is similar to OLED technology and the same materials (like MEH-PPV) can be used, here is a picture of one of them : (MEH-PPV laser pumped by a microchip laser)

This picture comes from St Andrew university (OSC) and I let you take a look on our link page to find more information inside the R&D laboratory website.