Ambipolar Charge Transport in p-Type Cyclopentadithiophene-Based Polymer Semiconductors Enabled by D–A–A–D Configuration

Polymer semiconductors with hysteresis-free ambipolar charge transport characteristics are key elements for developing high-performance organic field-effect transistors and circuits. In this study, a new and facile strategy of simply reconfiguring the donor (D) and acceptor (A) moieties in the order D–A–A–D in the repeat units was proposed to prepare D–A-type polymer semiconductors with enhanced electron and hole mobilities and hysteresis-free transistor characteristics. In contrast to the conventional D–A-type polymer semiconductor based on cyclopentadithiophene (CDT) and pyridyl-2,1,3-thiadiazole (PT) (hereafter, PCDTPT), the newly developed polymer with CDT–PT–PT–CDT configuration (hereafter, PCPPC) exhibited hysteresis-free transistor characteristics and enhanced electron and hole mobilities of 0.41 and 1.50 cm 2 V –1 s –1, respectively. Such improvements were attributed to the deepened conduction band edge of PCPPC compared with that of its D–A-type counterpart, PCDTPT. Owing to the improved ambipolar charge-transport characteristics, the organic complementary metal-oxide semiconductor inverters fabricated with the PCPPC charge transporting layers exhibited a remarkably high gain of greater than 165. Our results provided a simple but effective strategy for designing high-performance ambipolar polymer semiconductors.