Since organic semiconducting polymers are sensitive to charge traps (CT), in recent years, an additional research focus has been related to identifying methods to reduce CT, particularly in organic field-effect transistor (OFET) devices. One approach to reduce CT is through surface passivation prior to semiconductor deposition. Previous studies have shown that passivated surfaces with different surfaces energies would greatly affect grain sizes and thin film surface morphologies. Nevertheless, the reasons why certain processing conditions and surface passivation can enhance OFET performance remain unclear. To further elucidate the origins of the effects, a series of experiments have been conducted to understand the mechanism. Herein, we have fabricated OFETs with a series of polymers including PDPP4Tz and PNDI2Tz, and the benchmark “N2200” as our model polymers. Common surface treatment chemicals (OTS, HMDS and PTS) were used. Structure-process-property links between surface treatment chemical structure and treatment methods have been studied. Herein, we report enhanced conjugated polymer nanofiber formation on modified dielectric layers, which positively affects OFET device performance. Polymer nanofiber (PN) networks were observed within thin films processed via solution shearing on OTS coated surfaces. With PNDI2Tz, OEFTs with mobilities as high as 0.08 cm2V-1s-1 were fabricated. We discovered that the formation of PN on low energy surfaces is due to the synergistic effects of solution shearing and surface energy optimization. By systematically analyzing polymer thin film morphologies, we are able to provide a mechanistic explanation of previously reported results of performance enhancements in OFETs. The mechanistic insight derived from this study can play an important role in the design of materials and processes for the large scale fabrication of soft electronics on various surfaces.

Enhanced conjugated polymer nanofiber network formation by synergistic effect of solution shearing and dielectric layer modification

255th National Meeting (2018)

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