Leveraging TIPS-assisted one-pot di-bromination for thiazole-flanked NDI and PDI conjugated n-type semiconductors

Abstract

High-performance unipolar n-type semiconductors are essential for advancing organic electronics. This study explores the impact of fluorination on thiazole-flanked naphthalenediimide (NDI) and perylenediimide (PDI) copolymers with benzothiadiazole (BT) acceptors. A novel one-pot bromination strategy enabled efficient synthesis of these electron-deficient monomers, which were subsequently copolymerized with fluorinated and non-fluorinated BT units. Optical and electrochemical analyses revealed that fluorination systematically lowers the LUMO energy levels, enhancing charge injection and n-type behavior. Fluorine substitution also influences molecular packing, as evidenced by UV-Vis absorption shifts, cyclic voltammetry, and grazing-incidence wide-angle X-ray scattering (GIWAXS). While moderate fluorination improves electron mobility by promoting backbone planarity and π–π stacking, excessive substitution disrupts molecular ordering, reducing charge transport efficiency. The optimized fluorinated copolymers exhibit electron mobilities up to 1.3 × 10⁻³ cm² V⁻¹ s⁻¹, demonstrating the potential of fluorination in tuning electronic properties for next-generation hybrid organic semiconductors.