A facile end-capping strategy with strong electron withdrawing groups for enhancing field-effect mobility†

Optimizing energy levels and molecular packing is critical for the development of high-mobility polymer semiconductors. However, this is generally challenged by complicated molecular engineering and synthetic procedures. In this study, we propose a facile “strong electron-withdrawing group end-capping” strategy to design high-mobility polymer semiconductors. This approach effectively lowers LUMO energy levels and enhances the π–π stacking interactions of the polymers. Specifically, we demonstrate that the introduction of 2-(5,6-difluoro-3-oxo-2,3-dihydro-1H-inden-1-ylidene) malononitrile (2FIC) into the backbones of PDPPTT and PNDI2T yields polymers (PDPPTT-2FIC and PNDI2T-2FIC) with deeper LUMO energy levels and reduced π–π stacking distances, which facilitate both electron injection and interchain charge transport. Notably, PDPPTT-2FIC exhibits improved ambipolar performance, showing average hole and electron mobilities of 3.23 and 0.54 cm² V⁻¹ s⁻¹, respectively, in comparison to 1.92 and 0.26 cm² V⁻¹ s⁻¹ for PDPPTT. Similarly, PNDI2T-2FIC demonstrates enhanced n-type performance with an average electron mobility of 0.74 cm² V⁻¹ s⁻¹ compared to 0.39 cm² V⁻¹ s⁻¹ for PNDI2T. These findings establish a facile and feasible pathway for designing high-performance polymer semiconductors.