Study On The Improved Performances Of OFETs Based On Organic Semiconductors Induced By P-6P And P-4P

Driven by the potential applications in organic electronics, such as electronic paper, radio frequency identification, sensors, logic circuits, large scale IC, flexible displays, etc, organic field-effect transistors（OFETs） have attrac ted great attention due to their inherent advantages, including low power consumption, flexibility, wide variety of material, suitable for mass production and so on. Recently, the versatile applications in OFETs with novel organic semiconductors need to be developed considering a single variety of traditional P type and N type materials. In addition, the performances of the OFETs are mainly determined by the morphology and quality of organic thin films. The semiconductor thin films with highly ordered, large size and good continuity are advantageous to the carrier transport, which will enhance the performances of devices. Therefore, we introduced the para-sexiphenyl（p-6P） and para-quarterphenyl（p-4P） as the inducing layer materials into the traditional and new N type as well as P type OFETs devices. The results showed that the performances of the devices with inducing layer are greatly improved compared to those of the control devices without inducing layer. The main contents of this work are listed as follows:（1） We used p-6p as the inducing layer and fabricated the C₆0-OFETs. The field-effect saturation mobility and on/off current ratio of the optimized device were improved to 0.794 cm²/V s and 2.02×10⁴, respectively, which were both much higher than those of the control device by one order of magnitude. This improvement was attributed to that p-6P could induce C₆0 to form highly oriented and continuous film which resulted in the better injection and transport of the carriers.（2） We prepared the pentacene derivative films by spin-coating process, and investigated the performances of OFETs with this novel material as active layer. As a result, we also inserted the p-6P inducing layer into the devices and found that the optimal device’s mobility and on/off current ratio were enhanced to 0.2 cm²/V s and 10⁵, respectively, which were higher than those of the device without p-6P. The AFM and SEM morphology images showed that the smooth surface of pentacene derivative films presented a more regular molecule arrangement after the introduction of p-6P thin films, which would results in the performance improvement of the devices.（3） A novel derivative of perylene tetracarboxylic acid alkylene diamines（PEPEC） was used as the active layer to explore the electric properties of O FETs. The device without inducing layer exhibited the traditional field-effect under a certain gate bias（≤20V）. Moreover, we found that PEPTC-OFETs also presented a better performance after inserting a 6 nm p-4P film as inducing layer. We attributed this improvement to the high quality of crystallinity PEPTC film, which would be beneficial to the carrier transport and the device’s performance enhancement.（4） We prepared CuPc-OFETs devices with structure of Si/SiO₂/p-4P/CuPc/V₂O₅/Al. As a result, the mobility and on/off current ratio of the optimized device were improved to 5×10^-2 cm²/V s and 10⁴, respectively. We attributed these improvements to that p-4p inducing layer resulted in the better transport of the carriers and V₂O₅ modifying layers could tuned the height of the carrier injection barrier and reduced the contact resistance（Rc）. This simple and effective procedure will be a useful reference for the application of the Cu Pc-OFETs.