Research On The Effect Of Active Layer Doping On The Performance Of Solution-based OFETs

Organic field effect transistors(OFETs)have received widespread attention in flexible driving displays,sensor arrays and biological portable devices since being discovered and studied.Preparation of OFETs based on the solution method is favored because of its advantages of simple operation and relatively low requirements for preparation environment.The quality of active layer film is very important to the performance of the device.The organic semiconductor material used in this paper is poly(3-hexylthiophene)(P3HT).The polymer molecules are in a disorderly curled state during solution spin coating,which hinders the transport of charge carriers.Therefore,improving the crystallinity and arrangement order of P3HT molecular film formation is of great significance to improving the device performance.Based on the original process(P3HT solution concentration is lOmg/ml,spin-coating rotation speed is 1000rpm,time is 30s),this paper explores the optimal mixing ratio from two aspects of active layer material blending and poor solvent adding.1)When the insulating polymer PMMA with a mass ratio of 40wt.%is added to the P3HT solution,the(hole)carrier mobility of the device is increased from 0.0061cm2/Vs to 0.013cm2/Vs,and the threshold voltage is decreased from-5V to-2V.Observing the morphology of the film,it can be seen that the two matrixes were separated vertically and formed an interconnected charge transport network,which is conducive to carrier transport;2)When the oligomer molecule TIPS-Pentacene is added,the crystallinity of the polymer molecule is improved,and it is embedded in the polymer amorphous matrix to form an effective carrier transport path.When TIPS-Pentacene with a mass ratio of 90wt.%is added to the P3HT solution,the(hole)carrier mobility of the device is increased from 0.0061cm2/Vs to 0.0378cm2/Vs,and the threshold voltage is decreased from-5V to-2V.It is observed from the ultraviolet absorption spectrum that the absorption peak at ?=555nm is the strongest,and the absorption spectrum at ?=606nm has the most red shift.In the X-ray diffraction analysis spectrum,at this ratio,it can be observed that the organic semiconductor film has the strongest(001)peak intensity at 2?=5.3°and the FWHM is the smallest.P3HT molecules are more arranged in an edge-on structure.The grain size is the largest(372)and there are fewer defects in the grain gap;3)When the poor solvent absolute ethanol with a volume ratio of 10%is added to the P3HT solution,the P3HT molecules are arranged in fibrous shape,and the arrangement are more orderly.The crystallinity is improved,and the film is uniform.The(hole)carrier mobility of the device is increased from 0.0061cm2/Vs to 0.0723cm2/Vs,which is an increase of about an order of magnitude,and the performance of the device is improved.