Synthesis of Molecular and Polymeric Benzimidazoline-based N-Type Dopants

Molecular doping is a crucial technique for manipulating the electronic properties of Organic Semiconductors (OSCs). However, doping n-type OSCs requires dopants with very low ionization energy (< 3.6 eV), a feature that renders these species air-sensitive and thus hampers their solution processability. To address this challenge, kinetically stabilized dopants, such as N-DMBI-H, a thermally activated benzimidazoline-based n-dopant, are commonly used for in situ activation within OSC films. Although modifying the structure of N-DMBI-H could enhance control over doping characteristics such as energetics, kinetics, miscibility within the OSC phase, phase segregation/localization, and diffusion, reported structural variations are currently limited. This study aims to diversify the dopant portfolio by developing novel benzimidazoline-based derivatives, including both molecular and polymeric variants. We present a refined synthetic approach yielding a variety of DMBI-like molecules in high yields. Leveraging polyurethane chemistry, we designed dimeric n-dopants capable of forming hydrogen bonds, intending to enhance control over blend morphology. Additionally, we investigated the synthesis of polymeric n-dopants through direct polymerization of functionalized DMBI derivatives or grafting DMBI-like pendants onto a polymeric backbone. The resulting diversified dopant portfolio holds promise for advancing existing molecular doping strategies, offering new tools for tailoring the electronic properties of organic semiconductors.