Materials Design via Optimized Intramolecular Noncovalent Interactions for High-Performance Organic Semiconductors

Abstract

We report the design, synthesis, and implemention in semiconducting polymers of a novel head-to-head linkage containing the TRTOR (3-alkyl-3′-alkoxy-2,2′-bithiophene) donor subunit having a single strategically optimized, planarizing noncovalent S···O interaction. Diverse complementary thermal, optical, electrochemical, X-ray scattering, electrical, photovoltaic, and electron microscopic characterization techniques are applied to establish structure–property correlations in a TRTOR-based polymer series. In comparison to monomers having double S···O interactions, replacing one alkoxy substituent with a less electron-donating alkyl one yields TRTOR-based polymers with significantly depressed (0.2–0.3 eV) HOMOs. Furthermore, the weaker single S···O interaction and greater TRTOR steric encumberance enhances materials processability without sacrificing backbone planarity. From another perspective, TRTOR has comparable electronic properties to ring-fused 5H-dithieno[3,2-b:2′,3′-d]pyran (DTP) subunits, but a cen...