LAUSR

Conjugated polymer field‐effect transistors are emerging as an enabling technology for flexible electronics due to their excellent mechanical properties combined with sufficiently high charge‐carrier mobilities and compatibility with large‐area, low‐temperature processing. However, their electrical stability remains a concern. ON‐state (accumulation mode) bias‐stress instabilities in organic semiconductors have been widely studied, and multiple mitigation strategies have been suggested. In contrast, OFF‐state (depletion mode) bias‐stress instabilities remain poorly understood despite being crucial for many applications in which the transistors are held in their OFF‐state for most of the time. Here, a simple method of using an antisolvent treatment is presented to achieve significant improvements in OFF‐state bias‐stress and environmental stability as well as general device performance for one of the best performing polymers, solution‐processable indacenodithiophene‐co‐benzothiadiazole (IDT‐BT). IDT‐BT is weakly crystalline, and the notable improvements to an antisolvent‐induced, increased degree of crystallinity, resulting in a lower probability of electron trapping and the removal of charge traps is attributed. The work highlights the importance of the microstructure in weakly crystalline polymer films and offers a simple processing strategy for achieving the reliability required for applications in flexible electronics.