The Influence Of The Electrode Modification On The Performance Of Pentacene Organic Field-effect Transistors

Organic field-effect transistor(OFET) has attracted considerable attention for its potential applications in electronic devices such as radio-frequency identification(RFID) tags, flexible electronic circuit, sensors and electrically pumped organic lasers due to its light-weight, low-cost and compatible with flexible substrate. However, the commercialization of OFET, faces several technical obstacles. Compared to inorganic fied-effect transistors, the low mobility and high operation voltage restrict its use in many applications.Many of the above problems related to interfaces in OFET. This article focused on the interface modification between the semiconductor and the electrodes, where the charge injection and removal happened during device operation, to obtain high-performance devices. Specific contents are shown as follows:1. The effect of different polymeric materials, PMMA, PS, PVDF as the electrode buffer layer on the device performance was investigated. Compared to the control device, device performance with polymer buffer has been significantly improved. Moreover, the results showed that the device employing PMMA as the electrode buffer layer exhibited the highest hole mobility of 0.59 cm2/Vs, which was almost five times of the control one. Such effect was ascribed to the optimal surface energy and appropriate dielectric constant of PMMA, which was favorable for the growth of pentacene crystal and responsible for the highest performance of OFET using PMMA as the electrode buffer layer. The low contact resistance implied a good contact between the active layer and the electrode, thereby helping to improve the device performance.2. The effect of silk fibroin as an electrode buffer layer on the device performance was investigated, and the thickness of silk fibroin was optimized. The results showed that when the silk fibroin was employed as the electrode buffer layer, device performance has been significantly improved. As thickness of the silk fibroin reached 4 nm, the carrier mobility and saturation current of the device reached the maximum as 0.32 cm2/Vs and 32 μA, corresponding to the improvement by 2 folds and 3 folds compared to the control one, repectively. The contact resistance of the device was also reduced from 0.57 M??cm to 0.16 M??cm. The performance enhancement was ascribed to the crystallization improvement of pentacene on the silk fibroin compared to that on Au.3. The effect of hole transporting materials, m-MTDATA, TPD and SubPc as electrode buffer layer on the device performance was investigated. Compared to the control device, device performance with the hole transporting buffer has been significantly improved. This was mainly attributed to improved interfacial contact. As the different buffer layers presented different morphologies, densities of defects, and grain boundaries, the performance of the OFET with different buffer layers showed a very significant discrepancy. The optimizated hole transporting material as an electrode buffer layer in P type OFET was choosed to be SubPc, with a highest mobility of 0.26 cm2/Vs among these three kinds of devices.This paper provided a novel method of modifying organic field-effect transistors, making the foundation for high performance OFET.