Modulating Optoelectronic Performance Through Strategic Chlorine Substitution in Diketopyrrolopyrrole-Based Conjugated Polymers

Chlorinated conjugated polymers offer a comparable and cost-effective alternative to fluorinated counterparts in organic electronics, yet a versatile and strategic regulation and optimization approach of their organic field-effect transistors (OFETs) performance remains underexplored. Herein, we report the rational design and synthesis of three chlorinated diketopyrrolopyrrole (DPP)-based copolymers (<b>PDPP-TBT</b>, <b>PDPP-TBTCl</b>, and <b>PDPP-TBTCl2</b>), and reveal the relationship between the molecular structure and OFETs performance. It was found that the reduction of chlorine in <b>PDPP-TBTCl</b> delivers attenuated hole mobilities of 0.011 cm² V^-1 s^-1 compared to that of <b>PDPP-TBTCl2</b> (0.003 cm² V^-1 s^-1). Computational investigations uncover that chlorine incorporation induces backbone distortion (from 0-42°), resulting in steric hindrance from chlorine atoms that disrupts polymer planarity reduces the highest occupied molecular orbital (HOMO) energy level (-5.49 eV for <b>PDPP-TBTCl</b>), and enhances thermal stability. This work provides critical insights into balancing electronic modulation and structural integrity in chlorinated conjugated polymers, paving the way for designing high-performance organic semiconductors through halogen engineering.