Synthesis and characterization of phenanthrocarbazole–diketopyrrolopyrrole copolymer for high‐performance field‐effect transistors

In this study, we successfully designed and synthesized a novel phenanthro1,10,9,8‐c,d,e,f,g]carbazole ( PCZ )‐based copolymer polyN‐(2‐octyldodecyl)‐4,8‐phenanthro1,10,9,8‐c,d,e,f,g]carbazole‐alt‐2,5‐dihexadecyl‐3,6‐di(thiophen‐2‐yl)pyrrolo3,4‐c]pyrrole‐1,4(2H,5H)‐dione] ( PPDPP ) with an extended π‐conjugation along the vertical orientation of polymer main chain. This polymer exhibited excellent solubility in common solvent and high thermal stability, owning good properties for solution‐processed field‐effect transistors (FETs). Besides, absorption spectra demonstrated that annealing PPDPP thin films led to obviously red‐shifted maxima, indicating the formations of aggregation or orderly π–π stacking in their solid‐state films. X‐ray diffraction measurements indicated the crystallinity of PPDPP thin films was enhanced after high temperature annealing, which was favorable for charge transport. The solution‐processed PPDPP ‐based FET devices were fabricated with a bottom‐gate/bottom‐contact geometry. A high hole mobility of up to 0.30 cm²/Vs and a current on/off ratio above 10⁵ had been demonstrated. These results indicated that the copolymers constructed by this kind of ladder‐type cores could be promising organic semiconductors for high‐performance FET applications. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013