Rational Design of n-Type Near-Amorphous Conjugated Polymers through Acceptor Modulation and Terpolymerization

Abstract

The design and synthesis of high-mobility n-type near-amorphous conjugated polymers (NACPs) represent a prominent research focus in organic semiconductors. The diketopyrrolopyrrole (DPP) unit is a widely used building block for constructing high-mobility conjugated polymers. However, DPP-based polymers often exhibit semi-crystalline structures and inherent p-type charge-transport characteristics, which hinder their application in n-type flexible electronic devices. To overcome these challenges, this study employs acceptor modulation and terpolymerization by integrating pyridine-flanked DPP with 3,4-difluorothiophene (2FT) and selenophene (Se) as comonomers. Besides, the incorporation of oligo(ethylene glycol) side chains is strategically designed to enhance polymer solubility and favorably modulate the morphology. Thus, a series of polymers, P2FTx (x = 100–0), are synthesized via Stille polycondensation, enabling systematic investigation of the composition-structure-property relationships. It reveals that optimal Se incorporation minimizes torsional barriers and reduces backbone regularity, inducing a near-amorphous phase with locally ordered domains while maintaining suitable energy levels for efficient electron transport. Notably, P2FT90 achieves the highest electron mobility of 0.47 cm²·V^-1·s^-1, highlighting the efficacy of this compositional engineering approach. This study exemplifies a synergistic approach that combines precise control of backbone regioregularity and energy-level engineering to realize high-performance n-type NACPs.

Keywords

Regioregularity / Organic field-effect transistors / Diketopyrrolopyrrole / Conjugated polymers / Charge transport / π–π Stacking / Amorphous materials / Donor-acceptor systems

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