Study On The Effect Of Electrode Modification On The Performance Of OFETs

As an organic device,the field effect transistor has been widely concerned and developed because of its excellent characteri stics which are different from those without orgainc parts.With the continuous optimization of OFETs device structure and the development of new organic material technology,organic devices have excellent performance in biomedicine,photoelectric detection,flexible display and so on.There is still a big gap between the device performance of OFETs and that of FET,in which the interface problem in the device is an important reason that limits the development of OFETs.In this paper,the research on the interface problem is mainly in two aspects.The first is the interface between the dielectric layer and the organic layer.The conductive channel of OFETs is generated at this interface,so the quality of the organic layer growth at this interface will directly affect the performance of the device.The second is the contact interface between the electrode and the organic layer,and there is a high contact barrier due to the mismatch of the work function between the electrode and the organic layer.In addition,there is a height difference between the electrode and the dielectric layer in the bottom contact structure,which is not conducive to the growth of the organic layer at the contact site.In the OFETs with bottom contact structure,the contact between the electrode and the organic semiconductor is affected by the substrate temperature,so the basic device is fabricated at different substrate temperature,and the device performance is the optimum when the substrate temperature is 70?.On this basis,HMDS is used to modify the device,and the performance of the basic device is the optimum when the substrate temperature is 70?.The carrier mobility reaches 1.64×10-2cm2/Vs,which is 8 times higher than that of the basic device at the same substrate temperature(2.39×10-3cm2/Vs),and 3 times higher than that of the device modified at 90?.This is attributed to the improvement of the growth of the organic layer in the channel after the HMDS modification,but almost no contribution to the interface between the electrode and the organic layer.The edge modification of Cu electrode by volatilization of PFBT was studied.Through the comparison of volatilization modification and immersion modification,it is found that the PFBT formed by volatilization modification is more beneficial to the growth of pentacene and the device performance is better.The comparison of only the edge modification and all the modification of the electrode was completed by means of volatilization modification.Under the two modification methods,the carrier mobility of the device is 2.9×10-3 cm2/Vs,and the maximum saturation current is 40 ?A.However,the contact resistance of all the electrode modified devices is lower than that of the edge modified devices,so the position of the conductive channel is inferred.Finally,on the basis of using PFBT modified electrode,OTS was used to modify the dielectric layer,and the mobility reached 2.39×10-2cm2/Vs,which was 8 times higher than that of the device modified only with PFBT(2.9×10-3cm2/Vs).Compared with the HMDS modified devices,the contact resistance is also significantly reduced.