Effect of Backbone Fluorine and Chlorine Substitution on Charge‐Transport Properties of Naphthalenediimide‐Based Polymer Semiconductors

Abstract Fluorine (F) and chlorine (Cl) substitution in organic semiconductors has been found to be effective for enhancing the performance of organic photovoltaics. However, the effect of these substitutions on charge transport properties of organic semiconductors remains elusive. A series of naphthalene diamide (NDI)‐based copolymers: N2200, the corresponding fluorinated N2200 (F‐N2200), and chlorinated N2200 (Cl‐N2200) are employed to fabricate field‐effect transistors. Gate‐dependent and temperature‐dependent mobility are measured and analyzed to reveal the intrinsic electronic properties of the polymers. It is found that F substitution decreases energetic disorder of the semiconductor while Cl substitution increases it. These findings are further supported by density functional theory calculations and characterizations on the performance of doped devices based on the three polymers. Overall, the influence of fluorination and chlorination on charge transport in those NDI‐based polymers is identified and clarified, which is important for justifying the wide employment of fluorination and chlorination strategies in organic electronics.